From 5f8de423f190bbb79a62f804151bc24824fa32d8 Mon Sep 17 00:00:00 2001
From: "Matt A. Tobin" <mattatobin@localhost.localdomain>
Date: Fri, 2 Feb 2018 04:16:08 -0500
Subject: Add m-esr52 at 52.6.0

---
 dom/events/ContentEventHandler.cpp | 3080 ++++++++++++++++++++++++++++++++++++
 1 file changed, 3080 insertions(+)
 create mode 100644 dom/events/ContentEventHandler.cpp

(limited to 'dom/events/ContentEventHandler.cpp')

diff --git a/dom/events/ContentEventHandler.cpp b/dom/events/ContentEventHandler.cpp
new file mode 100644
index 000000000..935ade23f
--- /dev/null
+++ b/dom/events/ContentEventHandler.cpp
@@ -0,0 +1,3080 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "ContentEventHandler.h"
+#include "mozilla/IMEStateManager.h"
+#include "mozilla/TextComposition.h"
+#include "mozilla/TextEvents.h"
+#include "mozilla/dom/Element.h"
+#include "mozilla/dom/HTMLUnknownElement.h"
+#include "mozilla/dom/Selection.h"
+#include "nsCaret.h"
+#include "nsCOMPtr.h"
+#include "nsContentUtils.h"
+#include "nsCopySupport.h"
+#include "nsFocusManager.h"
+#include "nsFontMetrics.h"
+#include "nsFrameSelection.h"
+#include "nsIContentIterator.h"
+#include "nsIPresShell.h"
+#include "nsISelection.h"
+#include "nsIFrame.h"
+#include "nsIObjectFrame.h"
+#include "nsLayoutUtils.h"
+#include "nsPresContext.h"
+#include "nsQueryObject.h"
+#include "nsRange.h"
+#include "nsTextFragment.h"
+#include "nsTextFrame.h"
+#include "nsView.h"
+
+#include <algorithm>
+
+namespace mozilla {
+
+using namespace dom;
+using namespace widget;
+
+/******************************************************************/
+/* ContentEventHandler                                            */
+/******************************************************************/
+
+// NOTE
+//
+// ContentEventHandler *creates* ranges as following rules:
+// 1. Start of range:
+//   1.1. Cases: [textNode or text[Node or textNode[
+//        When text node is start of a range, start node is the text node and
+//        start offset is any number between 0 and the length of the text.
+//   1.2. Case: [<element>:
+//        When start of an element node is start of a range, start node is
+//        parent of the element and start offset is the element's index in the
+//        parent.
+//   1.3. Case: <element/>[
+//        When after an empty element node is start of a range, start node is
+//        parent of the element and start offset is the element's index in the
+//        parent + 1.
+//   1.4. Case: <element>[
+//        When start of a non-empty element is start of a range, start node is
+//        the element and start offset is 0.
+//   1.5. Case: <root>[
+//        When start of a range is 0 and there are no nodes causing text,
+//        start node is the root node and start offset is 0.
+//   1.6. Case: [</root>
+//        When start of a range is out of bounds, start node is the root node
+//        and start offset is number of the children.
+// 2. End of range:
+//   2.1. Cases: ]textNode or text]Node or textNode]
+//        When a text node is end of a range, end node is the text node and
+//        end offset is any number between 0 and the length of the text.
+//   2.2. Case: ]<element>
+//        When before an element node (meaning before the open tag of the
+//        element) is end of a range, end node is previous node causing text.
+//        Note that this case shouldn't be handled directly.  If rule 2.1 and
+//        2.3 are handled correctly, the loop with nsContentIterator shouldn't
+//        reach the element node since the loop should've finished already at
+//        handling the last node which caused some text.
+//   2.3. Case: <element>]
+//        When a line break is caused before a non-empty element node and it's
+//        end of a range, end node is the element and end offset is 0.
+//        (i.e., including open tag of the element)
+//   2.4. Cases: <element/>]
+//        When after an empty element node is end of a range, end node is
+//        parent of the element node and end offset is the element's index in
+//        the parent + 1.  (i.e., including close tag of the element or empty
+//        element)
+//   2.5. Case: ]</root>
+//        When end of a range is out of bounds, end node is the root node and
+//        end offset is number of the children.
+//
+// ContentEventHandler *treats* ranges as following additional rules:
+// 1. When the start node is an element node which doesn't have children,
+//    it includes a line break caused before itself (i.e., includes its open
+//    tag).  For example, if start position is { <br>, 0 }, the line break
+//    caused by <br> should be included into the flatten text.
+// 2. When the end node is an element node which doesn't have children,
+//    it includes the end (i.e., includes its close tag except empty element).
+//    Although, currently, any close tags don't cause line break, this also
+//    includes its open tag.  For example, if end position is { <br>, 0 }, the
+//    line break caused by the <br> should be included into the flatten text.
+
+ContentEventHandler::ContentEventHandler(nsPresContext* aPresContext)
+  : mPresContext(aPresContext)
+  , mPresShell(aPresContext->GetPresShell())
+  , mSelection(nullptr)
+  , mFirstSelectedRange(nullptr)
+  , mRootContent(nullptr)
+{
+}
+
+nsresult
+ContentEventHandler::InitBasic()
+{
+  NS_ENSURE_TRUE(mPresShell, NS_ERROR_NOT_AVAILABLE);
+
+  // If text frame which has overflowing selection underline is dirty,
+  // we need to flush the pending reflow here.
+  mPresShell->FlushPendingNotifications(Flush_Layout);
+
+  // Flushing notifications can cause mPresShell to be destroyed (bug 577963).
+  NS_ENSURE_TRUE(!mPresShell->IsDestroying(), NS_ERROR_FAILURE);
+
+  return NS_OK;
+}
+
+nsresult
+ContentEventHandler::InitRootContent(Selection* aNormalSelection)
+{
+  MOZ_ASSERT(aNormalSelection);
+
+  // Root content should be computed with normal selection because normal
+  // selection is typically has at least one range but the other selections
+  // not so.  If there is a range, computing its root is easy, but if
+  // there are no ranges, we need to use ancestor limit instead.
+  MOZ_ASSERT(aNormalSelection->Type() == SelectionType::eNormal);
+
+  if (!aNormalSelection->RangeCount()) {
+    // If there is no selection range, we should compute the selection root
+    // from ancestor limiter or root content of the document.
+    nsresult rv =
+      aNormalSelection->GetAncestorLimiter(getter_AddRefs(mRootContent));
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return NS_ERROR_FAILURE;
+    }
+    if (!mRootContent) {
+      mRootContent = mPresShell->GetDocument()->GetRootElement();
+      if (NS_WARN_IF(!mRootContent)) {
+        return NS_ERROR_NOT_AVAILABLE;
+      }
+    }
+    return NS_OK;
+  }
+
+  RefPtr<nsRange> range(aNormalSelection->GetRangeAt(0));
+  if (NS_WARN_IF(!range)) {
+    return NS_ERROR_UNEXPECTED;
+  }
+
+  // If there is a selection, we should retrieve the selection root from
+  // the range since when the window is inactivated, the ancestor limiter
+  // of selection was cleared by blur event handler of EditorBase but the
+  // selection range still keeps storing the nodes.  If the active element of
+  // the deactive window is <input> or <textarea>, we can compute the
+  // selection root from them.
+  nsINode* startNode = range->GetStartParent();
+  nsINode* endNode = range->GetEndParent();
+  if (NS_WARN_IF(!startNode) || NS_WARN_IF(!endNode)) {
+    return NS_ERROR_FAILURE;
+  }
+
+  // See bug 537041 comment 5, the range could have removed node.
+  if (NS_WARN_IF(startNode->GetUncomposedDoc() != mPresShell->GetDocument())) {
+    return NS_ERROR_FAILURE;
+  }
+
+  NS_ASSERTION(startNode->GetUncomposedDoc() == endNode->GetUncomposedDoc(),
+               "firstNormalSelectionRange crosses the document boundary");
+
+  mRootContent = startNode->GetSelectionRootContent(mPresShell);
+  if (NS_WARN_IF(!mRootContent)) {
+    return NS_ERROR_FAILURE;
+  }
+
+  return NS_OK;
+}
+
+nsresult
+ContentEventHandler::InitCommon(SelectionType aSelectionType)
+{
+  if (mSelection && mSelection->Type() == aSelectionType) {
+    return NS_OK;
+  }
+
+  mSelection = nullptr;
+  mFirstSelectedRange = nullptr;
+  mRootContent = nullptr;
+
+  nsresult rv = InitBasic();
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  nsCOMPtr<nsISelectionController> selectionController =
+    mPresShell->GetSelectionControllerForFocusedContent();
+  if (NS_WARN_IF(!selectionController)) {
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+  nsCOMPtr<nsISelection> selection;
+  rv = selectionController->GetSelection(ToRawSelectionType(aSelectionType),
+                                         getter_AddRefs(selection));
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return NS_ERROR_UNEXPECTED;
+  }
+
+  mSelection = static_cast<Selection*>(selection.get());
+  if (NS_WARN_IF(!mSelection)) {
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+
+  RefPtr<Selection> normalSelection;
+  if (mSelection->Type() == SelectionType::eNormal) {
+    normalSelection = mSelection;
+  } else {
+    nsCOMPtr<nsISelection> domSelection;
+    nsresult rv =
+      selectionController->GetSelection(
+                             nsISelectionController::SELECTION_NORMAL,
+                             getter_AddRefs(domSelection));
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return NS_ERROR_UNEXPECTED;
+    }
+    if (NS_WARN_IF(!domSelection)) {
+      return NS_ERROR_NOT_AVAILABLE;
+    }
+    normalSelection = domSelection->AsSelection();
+    if (NS_WARN_IF(!normalSelection)) {
+      return NS_ERROR_NOT_AVAILABLE;
+    }
+  }
+
+  rv = InitRootContent(normalSelection);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  if (mSelection->RangeCount()) {
+    mFirstSelectedRange = mSelection->GetRangeAt(0);
+    if (NS_WARN_IF(!mFirstSelectedRange)) {
+      return NS_ERROR_UNEXPECTED;
+    }
+    return NS_OK;
+  }
+
+  // Even if there are no selection ranges, it's usual case if aSelectionType
+  // is a special selection.
+  if (aSelectionType != SelectionType::eNormal) {
+    MOZ_ASSERT(!mFirstSelectedRange);
+    return NS_OK;
+  }
+
+  // But otherwise, we need to assume that there is a selection range at the
+  // beginning of the root content if aSelectionType is eNormal.
+  rv = nsRange::CreateRange(mRootContent, 0, mRootContent, 0,
+                            getter_AddRefs(mFirstSelectedRange));
+  if (NS_WARN_IF(NS_FAILED(rv)) || NS_WARN_IF(!mFirstSelectedRange)) {
+    return NS_ERROR_UNEXPECTED;
+  }
+  return NS_OK;
+}
+
+nsresult
+ContentEventHandler::Init(WidgetQueryContentEvent* aEvent)
+{
+  NS_ASSERTION(aEvent, "aEvent must not be null");
+  MOZ_ASSERT(aEvent->mMessage == eQuerySelectedText ||
+             aEvent->mInput.mSelectionType == SelectionType::eNormal);
+
+  if (NS_WARN_IF(!aEvent->mInput.IsValidOffset()) ||
+      NS_WARN_IF(!aEvent->mInput.IsValidEventMessage(aEvent->mMessage))) {
+    return NS_ERROR_FAILURE;
+  }
+
+  // Note that we should ignore WidgetQueryContentEvent::Input::mSelectionType
+  // if the event isn't eQuerySelectedText.
+  SelectionType selectionType =
+    aEvent->mMessage == eQuerySelectedText ? aEvent->mInput.mSelectionType :
+                                             SelectionType::eNormal;
+  if (NS_WARN_IF(selectionType == SelectionType::eNone)) {
+    return NS_ERROR_FAILURE;
+  }
+
+  nsresult rv = InitCommon(selectionType);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  // Be aware, WidgetQueryContentEvent::mInput::mOffset should be made absolute
+  // offset before sending it to ContentEventHandler because querying selection
+  // every time may be expensive.  So, if the caller caches selection, it
+  // should initialize the event with the cached value.
+  if (aEvent->mInput.mRelativeToInsertionPoint) {
+    MOZ_ASSERT(selectionType == SelectionType::eNormal);
+    RefPtr<TextComposition> composition =
+      IMEStateManager::GetTextCompositionFor(aEvent->mWidget);
+    if (composition) {
+      uint32_t compositionStart = composition->NativeOffsetOfStartComposition();
+      if (NS_WARN_IF(!aEvent->mInput.MakeOffsetAbsolute(compositionStart))) {
+        return NS_ERROR_FAILURE;
+      }
+    } else {
+      LineBreakType lineBreakType = GetLineBreakType(aEvent);
+      uint32_t selectionStart = 0;
+      rv = GetStartOffset(mFirstSelectedRange, &selectionStart, lineBreakType);
+      if (NS_WARN_IF(NS_FAILED(rv))) {
+        return NS_ERROR_FAILURE;
+      }
+      if (NS_WARN_IF(!aEvent->mInput.MakeOffsetAbsolute(selectionStart))) {
+        return NS_ERROR_FAILURE;
+      }
+    }
+  }
+
+  aEvent->mSucceeded = false;
+
+  aEvent->mReply.mContentsRoot = mRootContent.get();
+
+  aEvent->mReply.mHasSelection = !mSelection->IsCollapsed();
+
+  nsRect r;
+  nsIFrame* frame = nsCaret::GetGeometry(mSelection, &r);
+  if (!frame) {
+    frame = mRootContent->GetPrimaryFrame();
+    if (NS_WARN_IF(!frame)) {
+      return NS_ERROR_FAILURE;
+    }
+  }
+  aEvent->mReply.mFocusedWidget = frame->GetNearestWidget();
+
+  return NS_OK;
+}
+
+nsresult
+ContentEventHandler::Init(WidgetSelectionEvent* aEvent)
+{
+  NS_ASSERTION(aEvent, "aEvent must not be null");
+
+  nsresult rv = InitCommon();
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  aEvent->mSucceeded = false;
+
+  return NS_OK;
+}
+
+nsIContent*
+ContentEventHandler::GetFocusedContent()
+{
+  nsIDocument* doc = mPresShell->GetDocument();
+  if (!doc) {
+    return nullptr;
+  }
+  nsCOMPtr<nsPIDOMWindowOuter> window = doc->GetWindow();
+  nsCOMPtr<nsPIDOMWindowOuter> focusedWindow;
+  return nsFocusManager::GetFocusedDescendant(window, true,
+                                              getter_AddRefs(focusedWindow));
+}
+
+bool
+ContentEventHandler::IsPlugin(nsIContent* aContent)
+{
+  return aContent &&
+         aContent->GetDesiredIMEState().mEnabled == IMEState::PLUGIN;
+}
+
+nsresult
+ContentEventHandler::QueryContentRect(nsIContent* aContent,
+                                      WidgetQueryContentEvent* aEvent)
+{
+  NS_PRECONDITION(aContent, "aContent must not be null");
+
+  nsIFrame* frame = aContent->GetPrimaryFrame();
+  NS_ENSURE_TRUE(frame, NS_ERROR_FAILURE);
+
+  // get rect for first frame
+  nsRect resultRect(nsPoint(0, 0), frame->GetRect().Size());
+  nsresult rv = ConvertToRootRelativeOffset(frame, resultRect);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  // account for any additional frames
+  while ((frame = frame->GetNextContinuation()) != nullptr) {
+    nsRect frameRect(nsPoint(0, 0), frame->GetRect().Size());
+    rv = ConvertToRootRelativeOffset(frame, frameRect);
+    NS_ENSURE_SUCCESS(rv, rv);
+    resultRect.UnionRect(resultRect, frameRect);
+  }
+
+  aEvent->mReply.mRect = LayoutDeviceIntRect::FromUnknownRect(
+      resultRect.ToOutsidePixels(mPresContext->AppUnitsPerDevPixel()));
+  // Returning empty rect may cause native IME confused, let's make sure to
+  // return non-empty rect.
+  EnsureNonEmptyRect(aEvent->mReply.mRect);
+  aEvent->mSucceeded = true;
+
+  return NS_OK;
+}
+
+// Editor places a bogus BR node under its root content if the editor doesn't
+// have any text. This happens even for single line editors.
+// When we get text content and when we change the selection,
+// we don't want to include the bogus BRs at the end.
+static bool IsContentBR(nsIContent* aContent)
+{
+  return aContent->IsHTMLElement(nsGkAtoms::br) &&
+         !aContent->AttrValueIs(kNameSpaceID_None,
+                                nsGkAtoms::type,
+                                nsGkAtoms::moz,
+                                eIgnoreCase) &&
+         !aContent->AttrValueIs(kNameSpaceID_None,
+                                nsGkAtoms::mozeditorbogusnode,
+                                nsGkAtoms::_true,
+                                eIgnoreCase);
+}
+
+static bool IsMozBR(nsIContent* aContent)
+{
+  return aContent->IsHTMLElement(nsGkAtoms::br) && !IsContentBR(aContent);
+}
+
+static void ConvertToNativeNewlines(nsAFlatString& aString)
+{
+#if defined(XP_WIN)
+  aString.ReplaceSubstring(NS_LITERAL_STRING("\n"), NS_LITERAL_STRING("\r\n"));
+#endif
+}
+
+static void AppendString(nsAString& aString, nsIContent* aContent)
+{
+  NS_ASSERTION(aContent->IsNodeOfType(nsINode::eTEXT),
+               "aContent is not a text node!");
+  const nsTextFragment* text = aContent->GetText();
+  if (!text) {
+    return;
+  }
+  text->AppendTo(aString);
+}
+
+static void AppendSubString(nsAString& aString, nsIContent* aContent,
+                            uint32_t aXPOffset, uint32_t aXPLength)
+{
+  NS_ASSERTION(aContent->IsNodeOfType(nsINode::eTEXT),
+               "aContent is not a text node!");
+  const nsTextFragment* text = aContent->GetText();
+  if (!text) {
+    return;
+  }
+  text->AppendTo(aString, int32_t(aXPOffset), int32_t(aXPLength));
+}
+
+#if defined(XP_WIN)
+static uint32_t CountNewlinesInXPLength(nsIContent* aContent,
+                                        uint32_t aXPLength)
+{
+  NS_ASSERTION(aContent->IsNodeOfType(nsINode::eTEXT),
+               "aContent is not a text node!");
+  const nsTextFragment* text = aContent->GetText();
+  if (!text) {
+    return 0;
+  }
+  // For automated tests, we should abort on debug build.
+  MOZ_ASSERT(aXPLength == UINT32_MAX || aXPLength <= text->GetLength(),
+             "aXPLength is out-of-bounds");
+  const uint32_t length = std::min(aXPLength, text->GetLength());
+  uint32_t newlines = 0;
+  for (uint32_t i = 0; i < length; ++i) {
+    if (text->CharAt(i) == '\n') {
+      ++newlines;
+    }
+  }
+  return newlines;
+}
+
+static uint32_t CountNewlinesInNativeLength(nsIContent* aContent,
+                                            uint32_t aNativeLength)
+{
+  NS_ASSERTION(aContent->IsNodeOfType(nsINode::eTEXT),
+               "aContent is not a text node!");
+  const nsTextFragment* text = aContent->GetText();
+  if (!text) {
+    return 0;
+  }
+  // For automated tests, we should abort on debug build.
+  MOZ_ASSERT(
+    (aNativeLength == UINT32_MAX || aNativeLength <= text->GetLength() * 2),
+    "aNativeLength is unexpected value");
+  const uint32_t xpLength = text->GetLength();
+  uint32_t newlines = 0;
+  for (uint32_t i = 0, nativeOffset = 0;
+       i < xpLength && nativeOffset < aNativeLength;
+       ++i, ++nativeOffset) {
+    // For automated tests, we should abort on debug build.
+    MOZ_ASSERT(i < text->GetLength(), "i is out-of-bounds");
+    if (text->CharAt(i) == '\n') {
+      ++newlines;
+      ++nativeOffset;
+    }
+  }
+  return newlines;
+}
+#endif
+
+/* static */ uint32_t
+ContentEventHandler::GetNativeTextLength(nsIContent* aContent,
+                                         uint32_t aStartOffset,
+                                         uint32_t aEndOffset)
+{
+  MOZ_ASSERT(aEndOffset >= aStartOffset,
+             "aEndOffset must be equals or larger than aStartOffset");
+  if (NS_WARN_IF(!aContent->IsNodeOfType(nsINode::eTEXT))) {
+    return 0;
+  }
+  if (aStartOffset == aEndOffset) {
+    return 0;
+  }
+  return GetTextLength(aContent, LINE_BREAK_TYPE_NATIVE, aEndOffset) -
+           GetTextLength(aContent, LINE_BREAK_TYPE_NATIVE, aStartOffset);
+}
+
+/* static */ uint32_t
+ContentEventHandler::GetNativeTextLength(nsIContent* aContent,
+                                         uint32_t aMaxLength)
+{
+  if (NS_WARN_IF(!aContent->IsNodeOfType(nsINode::eTEXT))) {
+    return 0;
+  }
+  return GetTextLength(aContent, LINE_BREAK_TYPE_NATIVE, aMaxLength);
+}
+
+/* static */ uint32_t
+ContentEventHandler::GetNativeTextLengthBefore(nsIContent* aContent,
+                                               nsINode* aRootNode)
+{
+  if (NS_WARN_IF(aContent->IsNodeOfType(nsINode::eTEXT))) {
+    return 0;
+  }
+  return ShouldBreakLineBefore(aContent, aRootNode) ?
+           GetBRLength(LINE_BREAK_TYPE_NATIVE) : 0;
+}
+
+/* static inline */ uint32_t
+ContentEventHandler::GetBRLength(LineBreakType aLineBreakType)
+{
+#if defined(XP_WIN)
+  // Length of \r\n
+  return (aLineBreakType == LINE_BREAK_TYPE_NATIVE) ? 2 : 1;
+#else
+  return 1;
+#endif
+}
+
+/* static */ uint32_t
+ContentEventHandler::GetTextLength(nsIContent* aContent,
+                                   LineBreakType aLineBreakType,
+                                   uint32_t aMaxLength)
+{
+  MOZ_ASSERT(aContent->IsNodeOfType(nsINode::eTEXT));
+
+  uint32_t textLengthDifference =
+#if defined(XP_WIN)
+    // On Windows, the length of a native newline ("\r\n") is twice the length
+    // of the XP newline ("\n"), so XP length is equal to the length of the
+    // native offset plus the number of newlines encountered in the string.
+    (aLineBreakType == LINE_BREAK_TYPE_NATIVE) ?
+      CountNewlinesInXPLength(aContent, aMaxLength) : 0;
+#else
+    // On other platforms, the native and XP newlines are the same.
+    0;
+#endif
+
+  const nsTextFragment* text = aContent->GetText();
+  if (!text) {
+    return 0;
+  }
+  uint32_t length = std::min(text->GetLength(), aMaxLength);
+  return length + textLengthDifference;
+}
+
+static uint32_t ConvertToXPOffset(nsIContent* aContent, uint32_t aNativeOffset)
+{
+#if defined(XP_WIN)
+  // On Windows, the length of a native newline ("\r\n") is twice the length of
+  // the XP newline ("\n"), so XP offset is equal to the length of the native
+  // offset minus the number of newlines encountered in the string.
+  return aNativeOffset - CountNewlinesInNativeLength(aContent, aNativeOffset);
+#else
+  // On other platforms, the native and XP newlines are the same.
+  return aNativeOffset;
+#endif
+}
+
+/* static */ bool
+ContentEventHandler::ShouldBreakLineBefore(nsIContent* aContent,
+                                           nsINode* aRootNode)
+{
+  // We don't need to append linebreak at the start of the root element.
+  if (aContent == aRootNode) {
+    return false;
+  }
+
+  // If it's not an HTML element (including other markup language's elements),
+  // we shouldn't insert like break before that for now.  Becoming this is a
+  // problem must be edge case.  E.g., when ContentEventHandler is used with
+  // MathML or SVG elements.
+  if (!aContent->IsHTMLElement()) {
+    return false;
+  }
+
+  // If the element is <br>, we need to check if the <br> is caused by web
+  // content.  Otherwise, i.e., it's caused by internal reason of Gecko,
+  // it shouldn't be exposed as a line break to flatten text.
+  if (aContent->IsHTMLElement(nsGkAtoms::br)) {
+    return IsContentBR(aContent);
+  }
+
+  // Note that ideally, we should refer the style of the primary frame of
+  // aContent for deciding if it's an inline.  However, it's difficult
+  // IMEContentObserver to notify IME of text change caused by style change.
+  // Therefore, currently, we should check only from the tag for now.
+  if (aContent->IsAnyOfHTMLElements(nsGkAtoms::a,
+                                    nsGkAtoms::abbr,
+                                    nsGkAtoms::acronym,
+                                    nsGkAtoms::b,
+                                    nsGkAtoms::bdi,
+                                    nsGkAtoms::bdo,
+                                    nsGkAtoms::big,
+                                    nsGkAtoms::cite,
+                                    nsGkAtoms::code,
+                                    nsGkAtoms::data,
+                                    nsGkAtoms::del,
+                                    nsGkAtoms::dfn,
+                                    nsGkAtoms::em,
+                                    nsGkAtoms::font,
+                                    nsGkAtoms::i,
+                                    nsGkAtoms::ins,
+                                    nsGkAtoms::kbd,
+                                    nsGkAtoms::mark,
+                                    nsGkAtoms::s,
+                                    nsGkAtoms::samp,
+                                    nsGkAtoms::small,
+                                    nsGkAtoms::span,
+                                    nsGkAtoms::strike,
+                                    nsGkAtoms::strong,
+                                    nsGkAtoms::sub,
+                                    nsGkAtoms::sup,
+                                    nsGkAtoms::time,
+                                    nsGkAtoms::tt,
+                                    nsGkAtoms::u,
+                                    nsGkAtoms::var)) {
+    return false;
+  }
+
+  // If the element is unknown element, we shouldn't insert line breaks before
+  // it since unknown elements should be ignored.
+  RefPtr<HTMLUnknownElement> unknownHTMLElement = do_QueryObject(aContent);
+  return !unknownHTMLElement;
+}
+
+nsresult
+ContentEventHandler::GenerateFlatTextContent(nsIContent* aContent,
+                                             nsAFlatString& aString,
+                                             LineBreakType aLineBreakType)
+{
+  MOZ_ASSERT(aString.IsEmpty());
+
+  RefPtr<nsRange> range = new nsRange(mRootContent);
+  ErrorResult rv;
+  range->SelectNodeContents(*aContent, rv);
+  if (NS_WARN_IF(rv.Failed())) {
+    return rv.StealNSResult();
+  }
+  return GenerateFlatTextContent(range, aString, aLineBreakType);
+}
+
+nsresult
+ContentEventHandler::GenerateFlatTextContent(nsRange* aRange,
+                                             nsAFlatString& aString,
+                                             LineBreakType aLineBreakType)
+{
+  MOZ_ASSERT(aString.IsEmpty());
+
+  if (aRange->Collapsed()) {
+    return NS_OK;
+  }
+
+  nsINode* startNode = aRange->GetStartParent();
+  nsINode* endNode = aRange->GetEndParent();
+  if (NS_WARN_IF(!startNode) || NS_WARN_IF(!endNode)) {
+    return NS_ERROR_FAILURE;
+  }
+
+  if (startNode == endNode && startNode->IsNodeOfType(nsINode::eTEXT)) {
+    nsIContent* content = startNode->AsContent();
+    AppendSubString(aString, content, aRange->StartOffset(),
+                    aRange->EndOffset() - aRange->StartOffset());
+    ConvertToNativeNewlines(aString);
+    return NS_OK;
+  }
+
+  nsCOMPtr<nsIContentIterator> iter = NS_NewPreContentIterator();
+  nsresult rv = iter->Init(aRange);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+  for (; !iter->IsDone(); iter->Next()) {
+    nsINode* node = iter->GetCurrentNode();
+    if (NS_WARN_IF(!node)) {
+      break;
+    }
+    if (!node->IsContent()) {
+      continue;
+    }
+    nsIContent* content = node->AsContent();
+
+    if (content->IsNodeOfType(nsINode::eTEXT)) {
+      if (content == startNode) {
+        AppendSubString(aString, content, aRange->StartOffset(),
+                        content->TextLength() - aRange->StartOffset());
+      } else if (content == endNode) {
+        AppendSubString(aString, content, 0, aRange->EndOffset());
+      } else {
+        AppendString(aString, content);
+      }
+    } else if (ShouldBreakLineBefore(content, mRootContent)) {
+      aString.Append(char16_t('\n'));
+    }
+  }
+  if (aLineBreakType == LINE_BREAK_TYPE_NATIVE) {
+    ConvertToNativeNewlines(aString);
+  }
+  return NS_OK;
+}
+
+static FontRange*
+AppendFontRange(nsTArray<FontRange>& aFontRanges, uint32_t aBaseOffset)
+{
+  FontRange* fontRange = aFontRanges.AppendElement();
+  fontRange->mStartOffset = aBaseOffset;
+  return fontRange;
+}
+
+/* static */ uint32_t
+ContentEventHandler::GetTextLengthInRange(nsIContent* aContent,
+                                          uint32_t aXPStartOffset,
+                                          uint32_t aXPEndOffset,
+                                          LineBreakType aLineBreakType)
+{
+  MOZ_ASSERT(aContent->IsNodeOfType(nsINode::eTEXT));
+
+  return aLineBreakType == LINE_BREAK_TYPE_NATIVE ?
+    GetNativeTextLength(aContent, aXPStartOffset, aXPEndOffset) :
+    aXPEndOffset - aXPStartOffset;
+}
+
+/* static */ void
+ContentEventHandler::AppendFontRanges(FontRangeArray& aFontRanges,
+                                      nsIContent* aContent,
+                                      int32_t aBaseOffset,
+                                      int32_t aXPStartOffset,
+                                      int32_t aXPEndOffset,
+                                      LineBreakType aLineBreakType)
+{
+  MOZ_ASSERT(aContent->IsNodeOfType(nsINode::eTEXT));
+
+  nsIFrame* frame = aContent->GetPrimaryFrame();
+  if (!frame) {
+    // It is a non-rendered content, create an empty range for it.
+    AppendFontRange(aFontRanges, aBaseOffset);
+    return;
+  }
+
+  int32_t baseOffset = aBaseOffset;
+  nsTextFrame* curr = do_QueryFrame(frame);
+  MOZ_ASSERT(curr, "Not a text frame");
+  while (curr) {
+    int32_t frameXPStart = std::max(curr->GetContentOffset(), aXPStartOffset);
+    int32_t frameXPEnd = std::min(curr->GetContentEnd(), aXPEndOffset);
+    if (frameXPStart >= frameXPEnd) {
+      curr = static_cast<nsTextFrame*>(curr->GetNextContinuation());
+      continue;
+    }
+
+    gfxSkipCharsIterator iter = curr->EnsureTextRun(nsTextFrame::eInflated);
+    gfxTextRun* textRun = curr->GetTextRun(nsTextFrame::eInflated);
+
+    nsTextFrame* next = nullptr;
+    if (frameXPEnd < aXPEndOffset) {
+      next = static_cast<nsTextFrame*>(curr->GetNextContinuation());
+      while (next && next->GetTextRun(nsTextFrame::eInflated) == textRun) {
+        frameXPEnd = std::min(next->GetContentEnd(), aXPEndOffset);
+        next = frameXPEnd < aXPEndOffset ?
+          static_cast<nsTextFrame*>(next->GetNextContinuation()) : nullptr;
+      }
+    }
+
+    gfxTextRun::Range skipRange(iter.ConvertOriginalToSkipped(frameXPStart),
+                                iter.ConvertOriginalToSkipped(frameXPEnd));
+    gfxTextRun::GlyphRunIterator runIter(textRun, skipRange);
+    int32_t lastXPEndOffset = frameXPStart;
+    while (runIter.NextRun()) {
+      gfxFont* font = runIter.GetGlyphRun()->mFont.get();
+      int32_t startXPOffset =
+        iter.ConvertSkippedToOriginal(runIter.GetStringStart());
+      // It is possible that the first glyph run has exceeded the frame,
+      // because the whole frame is filled by skipped chars.
+      if (startXPOffset >= frameXPEnd) {
+        break;
+      }
+
+      if (startXPOffset > lastXPEndOffset) {
+        // Create range for skipped leading chars.
+        AppendFontRange(aFontRanges, baseOffset);
+        baseOffset += GetTextLengthInRange(
+          aContent, lastXPEndOffset, startXPOffset, aLineBreakType);
+        lastXPEndOffset = startXPOffset;
+      }
+
+      FontRange* fontRange = AppendFontRange(aFontRanges, baseOffset);
+      fontRange->mFontName = font->GetName();
+      fontRange->mFontSize = font->GetAdjustedSize();
+
+      // The converted original offset may exceed the range,
+      // hence we need to clamp it.
+      int32_t endXPOffset =
+        iter.ConvertSkippedToOriginal(runIter.GetStringEnd());
+      endXPOffset = std::min(frameXPEnd, endXPOffset);
+      baseOffset += GetTextLengthInRange(aContent, startXPOffset, endXPOffset,
+                                         aLineBreakType);
+      lastXPEndOffset = endXPOffset;
+    }
+    if (lastXPEndOffset < frameXPEnd) {
+      // Create range for skipped trailing chars. It also handles case
+      // that the whole frame contains only skipped chars.
+      AppendFontRange(aFontRanges, baseOffset);
+      baseOffset += GetTextLengthInRange(
+        aContent, lastXPEndOffset, frameXPEnd, aLineBreakType);
+    }
+
+    curr = next;
+  }
+}
+
+nsresult
+ContentEventHandler::GenerateFlatFontRanges(nsRange* aRange,
+                                            FontRangeArray& aFontRanges,
+                                            uint32_t& aLength,
+                                            LineBreakType aLineBreakType)
+{
+  MOZ_ASSERT(aFontRanges.IsEmpty(), "aRanges must be empty array");
+
+  if (aRange->Collapsed()) {
+    return NS_OK;
+  }
+
+  nsINode* startNode = aRange->GetStartParent();
+  nsINode* endNode = aRange->GetEndParent();
+  if (NS_WARN_IF(!startNode) || NS_WARN_IF(!endNode)) {
+    return NS_ERROR_FAILURE;
+  }
+
+  // baseOffset is the flattened offset of each content node.
+  int32_t baseOffset = 0;
+  nsCOMPtr<nsIContentIterator> iter = NS_NewPreContentIterator();
+  nsresult rv = iter->Init(aRange);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+  for (; !iter->IsDone(); iter->Next()) {
+    nsINode* node = iter->GetCurrentNode();
+    if (NS_WARN_IF(!node)) {
+      break;
+    }
+    if (!node->IsContent()) {
+      continue;
+    }
+    nsIContent* content = node->AsContent();
+
+    if (content->IsNodeOfType(nsINode::eTEXT)) {
+      int32_t startOffset = content != startNode ? 0 : aRange->StartOffset();
+      int32_t endOffset = content != endNode ?
+        content->TextLength() : aRange->EndOffset();
+      AppendFontRanges(aFontRanges, content, baseOffset,
+                       startOffset, endOffset, aLineBreakType);
+      baseOffset += GetTextLengthInRange(content, startOffset, endOffset,
+                                         aLineBreakType);
+    } else if (ShouldBreakLineBefore(content, mRootContent)) {
+      if (aFontRanges.IsEmpty()) {
+        MOZ_ASSERT(baseOffset == 0);
+        FontRange* fontRange = AppendFontRange(aFontRanges, baseOffset);
+        nsIFrame* frame = content->GetPrimaryFrame();
+        if (frame) {
+          const nsFont& font = frame->GetParent()->StyleFont()->mFont;
+          const FontFamilyList& fontList = font.fontlist;
+          const FontFamilyName& fontName = fontList.IsEmpty() ?
+            FontFamilyName(fontList.GetDefaultFontType()) :
+            fontList.GetFontlist()[0];
+          fontName.AppendToString(fontRange->mFontName, false);
+          fontRange->mFontSize =
+            frame->PresContext()->AppUnitsToDevPixels(font.size);
+        }
+      }
+      baseOffset += GetBRLength(aLineBreakType);
+    }
+  }
+
+  aLength = baseOffset;
+  return NS_OK;
+}
+
+nsresult
+ContentEventHandler::ExpandToClusterBoundary(nsIContent* aContent,
+                                             bool aForward,
+                                             uint32_t* aXPOffset)
+{
+  // XXX This method assumes that the frame boundaries must be cluster
+  // boundaries. It's false, but no problem now, maybe.
+  if (!aContent->IsNodeOfType(nsINode::eTEXT) ||
+      *aXPOffset == 0 || *aXPOffset == aContent->TextLength()) {
+    return NS_OK;
+  }
+
+  NS_ASSERTION(*aXPOffset <= aContent->TextLength(),
+               "offset is out of range.");
+
+  RefPtr<nsFrameSelection> fs = mPresShell->FrameSelection();
+  int32_t offsetInFrame;
+  CaretAssociationHint hint =
+    aForward ? CARET_ASSOCIATE_BEFORE : CARET_ASSOCIATE_AFTER;
+  nsIFrame* frame = fs->GetFrameForNodeOffset(aContent, int32_t(*aXPOffset),
+                                              hint, &offsetInFrame);
+  if (!frame) {
+    // This content doesn't have any frames, we only can check surrogate pair...
+    const nsTextFragment* text = aContent->GetText();
+    NS_ENSURE_TRUE(text, NS_ERROR_FAILURE);
+    if (NS_IS_LOW_SURROGATE(text->CharAt(*aXPOffset)) &&
+        NS_IS_HIGH_SURROGATE(text->CharAt(*aXPOffset - 1))) {
+      *aXPOffset += aForward ? 1 : -1;
+    }
+    return NS_OK;
+  }
+  int32_t startOffset, endOffset;
+  nsresult rv = frame->GetOffsets(startOffset, endOffset);
+  NS_ENSURE_SUCCESS(rv, rv);
+  if (*aXPOffset == static_cast<uint32_t>(startOffset) ||
+      *aXPOffset == static_cast<uint32_t>(endOffset)) {
+    return NS_OK;
+  }
+  if (frame->GetType() != nsGkAtoms::textFrame) {
+    return NS_ERROR_FAILURE;
+  }
+  nsTextFrame* textFrame = static_cast<nsTextFrame*>(frame);
+  int32_t newOffsetInFrame = *aXPOffset - startOffset;
+  newOffsetInFrame += aForward ? -1 : 1;
+  textFrame->PeekOffsetCharacter(aForward, &newOffsetInFrame);
+  *aXPOffset = startOffset + newOffsetInFrame;
+  return NS_OK;
+}
+
+nsresult
+ContentEventHandler::SetRangeFromFlatTextOffset(nsRange* aRange,
+                                                uint32_t aOffset,
+                                                uint32_t aLength,
+                                                LineBreakType aLineBreakType,
+                                                bool aExpandToClusterBoundaries,
+                                                uint32_t* aNewOffset,
+                                                nsIContent** aLastTextNode)
+{
+  if (aNewOffset) {
+    *aNewOffset = aOffset;
+  }
+  if (aLastTextNode) {
+    *aLastTextNode = nullptr;
+  }
+
+  // Special case like <br contenteditable>
+  if (!mRootContent->HasChildren()) {
+    nsresult rv = aRange->SetStart(mRootContent, 0);
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return rv;
+    }
+    rv = aRange->SetEnd(mRootContent, 0);
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return rv;
+    }
+  }
+
+  nsCOMPtr<nsIContentIterator> iter = NS_NewPreContentIterator();
+  nsresult rv = iter->Init(mRootContent);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  uint32_t offset = 0;
+  uint32_t endOffset = aOffset + aLength;
+  bool startSet = false;
+  for (; !iter->IsDone(); iter->Next()) {
+    nsINode* node = iter->GetCurrentNode();
+    if (NS_WARN_IF(!node)) {
+      break;
+    }
+    // FYI: mRootContent shouldn't cause any text. So, we can skip it simply.
+    if (node == mRootContent || !node->IsContent()) {
+      continue;
+    }
+    nsIContent* content = node->AsContent();
+
+    if (aLastTextNode && content->IsNodeOfType(nsINode::eTEXT)) {
+      NS_IF_RELEASE(*aLastTextNode);
+      NS_ADDREF(*aLastTextNode = content);
+    }
+
+    uint32_t textLength =
+      content->IsNodeOfType(nsINode::eTEXT) ?
+        GetTextLength(content, aLineBreakType) :
+        (ShouldBreakLineBefore(content, mRootContent) ?
+           GetBRLength(aLineBreakType) : 0);
+    if (!textLength) {
+      continue;
+    }
+
+    // When the start offset is in between accumulated offset and the last
+    // offset of the node, the node is the start node of the range.
+    if (!startSet && aOffset <= offset + textLength) {
+      nsINode* startNode = nullptr;
+      int32_t startNodeOffset = -1;
+      if (content->IsNodeOfType(nsINode::eTEXT)) {
+        // Rule #1.1: [textNode or text[Node or textNode[
+        uint32_t xpOffset = aOffset - offset;
+        if (aLineBreakType == LINE_BREAK_TYPE_NATIVE) {
+          xpOffset = ConvertToXPOffset(content, xpOffset);
+        }
+
+        if (aExpandToClusterBoundaries) {
+          uint32_t oldXPOffset = xpOffset;
+          rv = ExpandToClusterBoundary(content, false, &xpOffset);
+          if (NS_WARN_IF(NS_FAILED(rv))) {
+            return rv;
+          }
+          if (aNewOffset) {
+            // This is correct since a cluster shouldn't include line break.
+            *aNewOffset -= (oldXPOffset - xpOffset);
+          }
+        }
+        startNode = content;
+        startNodeOffset = static_cast<int32_t>(xpOffset);
+      } else if (aOffset < offset + textLength) {
+        // Rule #1.2 [<element>
+        startNode = content->GetParent();
+        if (NS_WARN_IF(!startNode)) {
+          return NS_ERROR_FAILURE;
+        }
+        startNodeOffset = startNode->IndexOf(content);
+        if (NS_WARN_IF(startNodeOffset == -1)) {
+          // The content is being removed from the parent!
+          return NS_ERROR_FAILURE;
+        }
+      } else if (!content->HasChildren()) {
+        // Rule #1.3: <element/>[
+        startNode = content->GetParent();
+        if (NS_WARN_IF(!startNode)) {
+          return NS_ERROR_FAILURE;
+        }
+        startNodeOffset = startNode->IndexOf(content) + 1;
+        if (NS_WARN_IF(startNodeOffset == 0)) {
+          // The content is being removed from the parent!
+          return NS_ERROR_FAILURE;
+        }
+      } else {
+        // Rule #1.4: <element>[
+        startNode = content;
+        startNodeOffset = 0;
+      }
+      NS_ASSERTION(startNode, "startNode must not be nullptr");
+      NS_ASSERTION(startNodeOffset >= 0,
+                   "startNodeOffset must not be negative");
+      rv = aRange->SetStart(startNode, startNodeOffset);
+      if (NS_WARN_IF(NS_FAILED(rv))) {
+        return rv;
+      }
+      startSet = true;
+
+      if (!aLength) {
+        rv = aRange->SetEnd(startNode, startNodeOffset);
+        if (NS_WARN_IF(NS_FAILED(rv))) {
+          return rv;
+        }
+        return NS_OK;
+      }
+    }
+
+    // When the end offset is in the content, the node is the end node of the
+    // range.
+    if (endOffset <= offset + textLength) {
+      MOZ_ASSERT(startSet,
+        "The start of the range should've been set already");
+      if (content->IsNodeOfType(nsINode::eTEXT)) {
+        // Rule #2.1: ]textNode or text]Node or textNode]
+        uint32_t xpOffset = endOffset - offset;
+        if (aLineBreakType == LINE_BREAK_TYPE_NATIVE) {
+          uint32_t xpOffsetCurrent = ConvertToXPOffset(content, xpOffset);
+          if (xpOffset && GetBRLength(aLineBreakType) > 1) {
+            MOZ_ASSERT(GetBRLength(aLineBreakType) == 2);
+            uint32_t xpOffsetPre = ConvertToXPOffset(content, xpOffset - 1);
+            // If previous character's XP offset is same as current character's,
+            // it means that the end offset is between \r and \n.  So, the
+            // range end should be after the \n.
+            if (xpOffsetPre == xpOffsetCurrent) {
+              xpOffset = xpOffsetCurrent + 1;
+            } else {
+              xpOffset = xpOffsetCurrent;
+            }
+          }
+        }
+        if (aExpandToClusterBoundaries) {
+          rv = ExpandToClusterBoundary(content, true, &xpOffset);
+          if (NS_WARN_IF(NS_FAILED(rv))) {
+            return rv;
+          }
+        }
+        NS_ASSERTION(xpOffset <= INT32_MAX,
+          "The end node offset is too large");
+        rv = aRange->SetEnd(content, static_cast<int32_t>(xpOffset));
+        if (NS_WARN_IF(NS_FAILED(rv))) {
+          return rv;
+        }
+        return NS_OK;
+      }
+
+      if (endOffset == offset) {
+        // Rule #2.2: ]<element>
+        // NOTE: Please don't crash on release builds because it must be
+        //       overreaction but we shouldn't allow this bug when some
+        //       automated tests find this.
+        MOZ_ASSERT(false, "This case should've already been handled at "
+                          "the last node which caused some text");
+        return NS_ERROR_FAILURE;
+      }
+
+      if (content->HasChildren() &&
+          ShouldBreakLineBefore(content, mRootContent)) {
+        // Rule #2.3: </element>]
+        rv = aRange->SetEnd(content, 0);
+        if (NS_WARN_IF(NS_FAILED(rv))) {
+          return rv;
+        }
+        return NS_OK;
+      }
+
+      // Rule #2.4: <element/>]
+      nsINode* endNode = content->GetParent();
+      if (NS_WARN_IF(!endNode)) {
+        return NS_ERROR_FAILURE;
+      }
+      int32_t indexInParent = endNode->IndexOf(content);
+      if (NS_WARN_IF(indexInParent == -1)) {
+        // The content is being removed from the parent!
+        return NS_ERROR_FAILURE;
+      }
+      rv = aRange->SetEnd(endNode, indexInParent + 1);
+      if (NS_WARN_IF(NS_FAILED(rv))) {
+        return rv;
+      }
+      return NS_OK;
+    }
+
+    offset += textLength;
+  }
+
+  if (!startSet) {
+    MOZ_ASSERT(!mRootContent->IsNodeOfType(nsINode::eTEXT));
+    if (!offset) {
+      // Rule #1.5: <root>[</root>
+      // When there are no nodes causing text, the start of the DOM range
+      // should be start of the root node since clicking on such editor (e.g.,
+      // <div contenteditable><span></span></div>) sets caret to the start of
+      // the editor (i.e., before <span> in the example).
+      rv = aRange->SetStart(mRootContent, 0);
+      if (NS_WARN_IF(NS_FAILED(rv))) {
+        return rv;
+      }
+      if (!aLength) {
+        rv = aRange->SetEnd(mRootContent, 0);
+        if (NS_WARN_IF(NS_FAILED(rv))) {
+          return rv;
+        }
+        return NS_OK;
+      }
+    } else {
+      // Rule #1.5: [</root>
+      rv = aRange->SetStart(mRootContent,
+                     static_cast<int32_t>(mRootContent->GetChildCount()));
+      if (NS_WARN_IF(NS_FAILED(rv))) {
+        return rv;
+      }
+    }
+    if (aNewOffset) {
+      *aNewOffset = offset;
+    }
+  }
+  // Rule #2.5: ]</root>
+  rv = aRange->SetEnd(mRootContent,
+                      static_cast<int32_t>(mRootContent->GetChildCount()));
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+  return NS_OK;
+}
+
+/* static */ LineBreakType
+ContentEventHandler::GetLineBreakType(WidgetQueryContentEvent* aEvent)
+{
+  return GetLineBreakType(aEvent->mUseNativeLineBreak);
+}
+
+/* static */ LineBreakType
+ContentEventHandler::GetLineBreakType(WidgetSelectionEvent* aEvent)
+{
+  return GetLineBreakType(aEvent->mUseNativeLineBreak);
+}
+
+/* static */ LineBreakType
+ContentEventHandler::GetLineBreakType(bool aUseNativeLineBreak)
+{
+  return aUseNativeLineBreak ?
+    LINE_BREAK_TYPE_NATIVE : LINE_BREAK_TYPE_XP;
+}
+
+nsresult
+ContentEventHandler::HandleQueryContentEvent(WidgetQueryContentEvent* aEvent)
+{
+  switch (aEvent->mMessage) {
+    case eQuerySelectedText:
+      return OnQuerySelectedText(aEvent);
+    case eQueryTextContent:
+      return OnQueryTextContent(aEvent);
+    case eQueryCaretRect:
+      return OnQueryCaretRect(aEvent);
+    case eQueryTextRect:
+      return OnQueryTextRect(aEvent);
+    case eQueryTextRectArray:
+      return OnQueryTextRectArray(aEvent);
+    case eQueryEditorRect:
+      return OnQueryEditorRect(aEvent);
+    case eQueryContentState:
+      return OnQueryContentState(aEvent);
+    case eQuerySelectionAsTransferable:
+      return OnQuerySelectionAsTransferable(aEvent);
+    case eQueryCharacterAtPoint:
+      return OnQueryCharacterAtPoint(aEvent);
+    case eQueryDOMWidgetHittest:
+      return OnQueryDOMWidgetHittest(aEvent);
+    default:
+      return NS_ERROR_NOT_IMPLEMENTED;
+  }
+  return NS_OK;
+}
+
+// Similar to nsFrameSelection::GetFrameForNodeOffset,
+// but this is more flexible for OnQueryTextRect to use
+static nsresult GetFrameForTextRect(nsINode* aNode,
+                                    int32_t aNodeOffset,
+                                    bool aHint,
+                                    nsIFrame** aReturnFrame)
+{
+  NS_ENSURE_TRUE(aNode && aNode->IsNodeOfType(nsINode::eCONTENT),
+                 NS_ERROR_UNEXPECTED);
+  nsIContent* content = static_cast<nsIContent*>(aNode);
+  nsIFrame* frame = content->GetPrimaryFrame();
+  NS_ENSURE_TRUE(frame, NS_ERROR_FAILURE);
+  int32_t childNodeOffset = 0;
+  return frame->GetChildFrameContainingOffset(aNodeOffset, aHint,
+                                              &childNodeOffset, aReturnFrame);
+}
+
+nsresult
+ContentEventHandler::OnQuerySelectedText(WidgetQueryContentEvent* aEvent)
+{
+  nsresult rv = Init(aEvent);
+  if (NS_FAILED(rv)) {
+    return rv;
+  }
+
+  if (!mFirstSelectedRange) {
+    MOZ_ASSERT(aEvent->mInput.mSelectionType != SelectionType::eNormal);
+    MOZ_ASSERT(aEvent->mReply.mOffset == WidgetQueryContentEvent::NOT_FOUND);
+    MOZ_ASSERT(aEvent->mReply.mString.IsEmpty());
+    MOZ_ASSERT(!aEvent->mReply.mHasSelection);
+    aEvent->mSucceeded = true;
+    return NS_OK;
+  }
+
+  nsINode* const startNode = mFirstSelectedRange->GetStartParent();
+  nsINode* const endNode = mFirstSelectedRange->GetEndParent();
+
+  // Make sure the selection is within the root content range.
+  if (!nsContentUtils::ContentIsDescendantOf(startNode, mRootContent) ||
+      !nsContentUtils::ContentIsDescendantOf(endNode, mRootContent)) {
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+
+  NS_ASSERTION(aEvent->mReply.mString.IsEmpty(),
+               "The reply string must be empty");
+
+  LineBreakType lineBreakType = GetLineBreakType(aEvent);
+  rv = GetStartOffset(mFirstSelectedRange,
+                      &aEvent->mReply.mOffset, lineBreakType);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  nsCOMPtr<nsINode> anchorNode, focusNode;
+  int32_t anchorOffset = 0, focusOffset = 0;
+  if (mSelection->RangeCount()) {
+    // If there is only one selection range, the anchor/focus node and offset
+    // are the information of the range.  Therefore, we have the direction
+    // information.
+    if (mSelection->RangeCount() == 1) {
+      anchorNode = mSelection->GetAnchorNode();
+      focusNode = mSelection->GetFocusNode();
+      if (NS_WARN_IF(!anchorNode) || NS_WARN_IF(!focusNode)) {
+        return NS_ERROR_FAILURE;
+      }
+      anchorOffset = static_cast<int32_t>(mSelection->AnchorOffset());
+      focusOffset = static_cast<int32_t>(mSelection->FocusOffset());
+      if (NS_WARN_IF(anchorOffset < 0) || NS_WARN_IF(focusOffset < 0)) {
+        return NS_ERROR_FAILURE;
+      }
+
+      int16_t compare = nsContentUtils::ComparePoints(anchorNode, anchorOffset,
+                                                      focusNode, focusOffset);
+      aEvent->mReply.mReversed = compare > 0;
+    }
+    // However, if there are 2 or more selection ranges, we have no information
+    // of that.
+    else {
+      aEvent->mReply.mReversed = false;
+    }
+
+    if (!mFirstSelectedRange->Collapsed()) {
+      rv = GenerateFlatTextContent(mFirstSelectedRange, aEvent->mReply.mString,
+                                   lineBreakType);
+      if (NS_WARN_IF(NS_FAILED(rv))) {
+        return rv;
+      }
+    } else {
+      aEvent->mReply.mString.Truncate();
+    }
+  } else {
+    NS_ASSERTION(mFirstSelectedRange->Collapsed(),
+      "When mSelection doesn't have selection, mFirstSelectedRange must be "
+      "collapsed");
+    anchorNode = focusNode = mFirstSelectedRange->GetStartParent();
+    if (NS_WARN_IF(!anchorNode)) {
+      return NS_ERROR_FAILURE;
+    }
+    anchorOffset = focusOffset =
+      static_cast<int32_t>(mFirstSelectedRange->StartOffset());
+    if (NS_WARN_IF(anchorOffset < 0)) {
+      return NS_ERROR_FAILURE;
+    }
+
+    aEvent->mReply.mReversed = false;
+    aEvent->mReply.mString.Truncate();
+  }
+
+
+  nsIFrame* frame = nullptr;
+  rv = GetFrameForTextRect(focusNode, focusOffset, true, &frame);
+  if (NS_SUCCEEDED(rv) && frame) {
+    aEvent->mReply.mWritingMode = frame->GetWritingMode();
+  } else {
+    aEvent->mReply.mWritingMode = WritingMode();
+  }
+
+  aEvent->mSucceeded = true;
+  return NS_OK;
+}
+
+nsresult
+ContentEventHandler::OnQueryTextContent(WidgetQueryContentEvent* aEvent)
+{
+  nsresult rv = Init(aEvent);
+  if (NS_FAILED(rv)) {
+    return rv;
+  }
+
+  NS_ASSERTION(aEvent->mReply.mString.IsEmpty(),
+               "The reply string must be empty");
+
+  LineBreakType lineBreakType = GetLineBreakType(aEvent);
+
+  RefPtr<nsRange> range = new nsRange(mRootContent);
+  rv = SetRangeFromFlatTextOffset(range, aEvent->mInput.mOffset,
+                                  aEvent->mInput.mLength, lineBreakType, false,
+                                  &aEvent->mReply.mOffset);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  rv = GenerateFlatTextContent(range, aEvent->mReply.mString, lineBreakType);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  if (aEvent->mWithFontRanges) {
+    uint32_t fontRangeLength;
+    rv = GenerateFlatFontRanges(range, aEvent->mReply.mFontRanges,
+                                fontRangeLength, lineBreakType);
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return rv;
+    }
+
+    MOZ_ASSERT(fontRangeLength == aEvent->mReply.mString.Length(),
+               "Font ranges doesn't match the string");
+  }
+
+  aEvent->mSucceeded = true;
+
+  return NS_OK;
+}
+
+void
+ContentEventHandler::EnsureNonEmptyRect(nsRect& aRect) const
+{
+  // See the comment in ContentEventHandler.h why this doesn't set them to
+  // one device pixel.
+  aRect.height = std::max(1, aRect.height);
+  aRect.width = std::max(1, aRect.width);
+}
+
+void
+ContentEventHandler::EnsureNonEmptyRect(LayoutDeviceIntRect& aRect) const
+{
+  aRect.height = std::max(1, aRect.height);
+  aRect.width = std::max(1, aRect.width);
+}
+
+ContentEventHandler::NodePosition
+ContentEventHandler::GetNodePositionHavingFlatText(
+                       const NodePosition& aNodePosition)
+{
+  return GetNodePositionHavingFlatText(aNodePosition.mNode,
+                                       aNodePosition.mOffset);
+}
+
+ContentEventHandler::NodePosition
+ContentEventHandler::GetNodePositionHavingFlatText(nsINode* aNode,
+                                                   int32_t aNodeOffset)
+{
+  if (aNode->IsNodeOfType(nsINode::eTEXT)) {
+    return NodePosition(aNode, aNodeOffset);
+  }
+
+  int32_t childCount = static_cast<int32_t>(aNode->GetChildCount());
+
+  // If it's a empty element node, returns itself.
+  if (!childCount) {
+    MOZ_ASSERT(!aNodeOffset || aNodeOffset == 1);
+    return NodePosition(aNode, aNodeOffset);
+  }
+
+  // If there is a node at given position, return the start of it.
+  if (aNodeOffset < childCount) {
+    return NodePosition(aNode->GetChildAt(aNodeOffset), 0);
+  }
+
+  // If the offset represents "after" the node, we need to return the last
+  // child of it.  For example, if a range is |<p>[<br>]</p>|, then, the
+  // end point is {<p>, 1}.  In such case, callers need the <br> node.
+  if (aNodeOffset == childCount) {
+    NodePosition result;
+    result.mNode = aNode->GetChildAt(childCount - 1);
+    result.mOffset = result.mNode->IsNodeOfType(nsINode::eTEXT) ?
+      static_cast<int32_t>(result.mNode->AsContent()->TextLength()) : 1;
+  }
+
+  NS_WARNING("aNodeOffset is invalid value");
+  return NodePosition();
+}
+
+ContentEventHandler::FrameAndNodeOffset
+ContentEventHandler::GetFirstFrameInRangeForTextRect(nsRange* aRange)
+{
+  NodePosition nodePosition;
+  nsCOMPtr<nsIContentIterator> iter = NS_NewPreContentIterator();
+  for (iter->Init(aRange); !iter->IsDone(); iter->Next()) {
+    nsINode* node = iter->GetCurrentNode();
+    if (NS_WARN_IF(!node)) {
+      break;
+    }
+
+    if (!node->IsContent()) {
+      continue;
+    }
+
+    if (node->IsNodeOfType(nsINode::eTEXT)) {
+      // If the range starts at the end of a text node, we need to find
+      // next node which causes text.
+      int32_t offsetInNode =
+        node == aRange->GetStartParent() ? aRange->StartOffset() : 0;
+      if (static_cast<uint32_t>(offsetInNode) < node->Length()) {
+        nodePosition.mNode = node;
+        nodePosition.mOffset = offsetInNode;
+        break;
+      }
+      continue;
+    }
+
+    // If the element node causes a line break before it, it's the first
+    // node causing text.
+    if (ShouldBreakLineBefore(node->AsContent(), mRootContent) ||
+        IsMozBR(node->AsContent())) {
+      nodePosition.mNode = node;
+      nodePosition.mOffset = 0;
+    }
+  }
+
+  if (!nodePosition.IsValid()) {
+    return FrameAndNodeOffset();
+  }
+
+  nsIFrame* firstFrame = nullptr;
+  GetFrameForTextRect(nodePosition.mNode, nodePosition.mOffset,
+                      true, &firstFrame);
+  return FrameAndNodeOffset(firstFrame, nodePosition.mOffset);
+}
+
+ContentEventHandler::FrameAndNodeOffset
+ContentEventHandler::GetLastFrameInRangeForTextRect(nsRange* aRange)
+{
+  NodePosition nodePosition;
+  nsCOMPtr<nsIContentIterator> iter = NS_NewPreContentIterator();
+  iter->Init(aRange);
+
+  nsINode* endNode = aRange->GetEndParent();
+  uint32_t endOffset = static_cast<uint32_t>(aRange->EndOffset());
+  // If the end point is start of a text node or specified by its parent and
+  // index, the node shouldn't be included into the range.  For example,
+  // with this case, |<p>abc[<br>]def</p>|, the range ends at 3rd children of
+  // <p> (see the range creation rules, "2.4. Cases: <element/>]"). This causes
+  // following frames:
+  // +----+-----+
+  // | abc|[<br>|
+  // +----+-----+
+  // +----+
+  // |]def|
+  // +----+
+  // So, if this method includes the 2nd text frame's rect to its result, the
+  // caller will return too tall rect which includes 2 lines in this case isn't
+  // expected by native IME  (e.g., popup of IME will be positioned at bottom
+  // of "d" instead of right-bottom of "c").  Therefore, this method shouldn't
+  // include the last frame when its content isn't really in aRange.
+  nsINode* nextNodeOfRangeEnd = nullptr;
+  if (endNode->IsNodeOfType(nsINode::eTEXT)) {
+    // Don't set nextNodeOfRangeEnd to the start node of aRange because if
+    // endNode is same as start node of the range, the text node shouldn't be
+    // next of range end even if the offset is 0.  This could occur with empty
+    // text node.
+    if (!endOffset && aRange->GetStartParent() != endNode) {
+      nextNodeOfRangeEnd = endNode;
+    }
+  } else if (endOffset < endNode->GetChildCount()) {
+    nextNodeOfRangeEnd = endNode->GetChildAt(endOffset);
+  }
+
+  for (iter->Last(); !iter->IsDone(); iter->Prev()) {
+    nsINode* node = iter->GetCurrentNode();
+    if (NS_WARN_IF(!node)) {
+      break;
+    }
+
+    if (!node->IsContent() || node == nextNodeOfRangeEnd) {
+      continue;
+    }
+
+    if (node->IsNodeOfType(nsINode::eTEXT)) {
+      nodePosition.mNode = node;
+      if (node == aRange->GetEndParent()) {
+        nodePosition.mOffset = aRange->EndOffset();
+      } else {
+        nodePosition.mOffset = node->Length();
+      }
+      // If the text node is empty or the last node of the range but the index
+      // is 0, we should store current position but continue looking for
+      // previous node (If there are no nodes before it, we should use current
+      // node position for returning its frame).
+      if (!nodePosition.mOffset) {
+        continue;
+      }
+      break;
+    }
+
+    if (ShouldBreakLineBefore(node->AsContent(), mRootContent) ||
+        IsMozBR(node->AsContent())) {
+      nodePosition.mNode = node;
+      nodePosition.mOffset = 0;
+      break;
+    }
+  }
+
+  if (!nodePosition.IsValid()) {
+    return FrameAndNodeOffset();
+  }
+
+  nsIFrame* lastFrame = nullptr;
+  GetFrameForTextRect(nodePosition.mNode, nodePosition.mOffset,
+                      true, &lastFrame);
+  if (!lastFrame) {
+    return FrameAndNodeOffset();
+  }
+
+  // If the last frame is a text frame, we need to check if the range actually
+  // includes at least one character in the range.  Therefore, if it's not a
+  // text frame, we need to do nothing anymore.
+  if (lastFrame->GetType() != nsGkAtoms::textFrame) {
+    return FrameAndNodeOffset(lastFrame, nodePosition.mOffset);
+  }
+
+  int32_t start, end;
+  if (NS_WARN_IF(NS_FAILED(lastFrame->GetOffsets(start, end)))) {
+    return FrameAndNodeOffset();
+  }
+
+  // If the start offset in the node is same as the computed offset in the
+  // node and it's not 0, the frame shouldn't be added to the text rect.  So,
+  // this should return previous text frame and its last offset if there is
+  // at least one text frame.
+  if (nodePosition.mOffset && nodePosition.mOffset == start) {
+    GetFrameForTextRect(nodePosition.mNode, --nodePosition.mOffset,
+                        true, &lastFrame);
+    if (NS_WARN_IF(!lastFrame)) {
+      return FrameAndNodeOffset();
+    }
+  }
+
+  return FrameAndNodeOffset(lastFrame, nodePosition.mOffset);
+}
+
+ContentEventHandler::FrameRelativeRect
+ContentEventHandler::GetLineBreakerRectBefore(nsIFrame* aFrame)
+{
+  // Note that this method should be called only with an element's frame whose
+  // open tag causes a line break or moz-<br> for computing empty last line's
+  // rect.
+  MOZ_ASSERT(ShouldBreakLineBefore(aFrame->GetContent(), mRootContent) ||
+             IsMozBR(aFrame->GetContent()));
+
+  nsIFrame* frameForFontMetrics = aFrame;
+
+  // If it's not a <br> frame, this method computes the line breaker's rect
+  // outside the frame.  Therefore, we need to compute with parent frame's
+  // font metrics in such case.
+  if (aFrame->GetType() != nsGkAtoms::brFrame && aFrame->GetParent()) {
+    frameForFontMetrics = aFrame->GetParent();
+  }
+
+  // Note that <br> element's rect is decided with line-height but we need
+  // a rect only with font height.  Additionally, <br> frame's width and
+  // height are 0 in quirks mode if it's not an empty line.  So, we cannot
+  // use frame rect information even if it's a <br> frame.
+
+  FrameRelativeRect result(aFrame);
+
+  RefPtr<nsFontMetrics> fontMetrics =
+    nsLayoutUtils::GetInflatedFontMetricsForFrame(frameForFontMetrics);
+  if (NS_WARN_IF(!fontMetrics)) {
+    return FrameRelativeRect();
+  }
+
+  const WritingMode kWritingMode = frameForFontMetrics->GetWritingMode();
+  nscoord baseline = aFrame->GetCaretBaseline();
+  if (kWritingMode.IsVertical()) {
+    if (kWritingMode.IsLineInverted()) {
+      result.mRect.x = baseline - fontMetrics->MaxDescent();
+    } else {
+      result.mRect.x = baseline - fontMetrics->MaxAscent();
+    }
+    result.mRect.width = fontMetrics->MaxHeight();
+  } else {
+    result.mRect.y = baseline - fontMetrics->MaxAscent();
+    result.mRect.height = fontMetrics->MaxHeight();
+  }
+
+  // If aFrame isn't a <br> frame, caret should be at outside of it because
+  // the line break is before its open tag.  For example, case of
+  // |<div><p>some text</p></div>|, caret is before <p> element and in <div>
+  // element, the caret should be left of top-left corner of <p> element like:
+  // 
+  // +-<div>-------------------  <div>'s border box
+  // | I +-<p>-----------------  <p>'s border box
+  // | I |
+  // | I |
+  // |   |
+  //   ^- caret
+  //
+  // However, this is a hack for unusual scenario.  This hack shouldn't be
+  // used as far as possible.
+  if (aFrame->GetType() != nsGkAtoms::brFrame) {
+    if (kWritingMode.IsVertical()) {
+      if (kWritingMode.IsLineInverted()) {
+        // above of top-left corner of aFrame.
+        result.mRect.x = 0;
+      } else {
+        // above of top-right corner of aFrame.
+        result.mRect.x = aFrame->GetRect().XMost() - result.mRect.width;
+      }
+      result.mRect.y = -mPresContext->AppUnitsPerDevPixel();
+    } else {
+      // left of top-left corner of aFrame.
+      result.mRect.x = -mPresContext->AppUnitsPerDevPixel();
+      result.mRect.y = 0;
+    }
+  }
+  return result;
+}
+
+ContentEventHandler::FrameRelativeRect
+ContentEventHandler::GuessLineBreakerRectAfter(nsIContent* aTextContent)
+{
+  // aTextContent should be a text node.
+  MOZ_ASSERT(aTextContent->IsNodeOfType(nsINode::eTEXT));
+
+  FrameRelativeRect result;
+  int32_t length = static_cast<int32_t>(aTextContent->Length());
+  if (NS_WARN_IF(length < 0)) {
+    return result;
+  }
+  // Get the last nsTextFrame which is caused by aTextContent.  Note that
+  // a text node can cause multiple text frames, e.g., the text is too long
+  // and wrapped by its parent block or the text has line breakers and its
+  // white-space property respects the line breakers (e.g., |pre|).
+  nsIFrame* lastTextFrame = nullptr;
+  nsresult rv = GetFrameForTextRect(aTextContent, length, true, &lastTextFrame);
+  if (NS_WARN_IF(NS_FAILED(rv)) || NS_WARN_IF(!lastTextFrame)) {
+    return result;
+  }
+  const nsRect kLastTextFrameRect = lastTextFrame->GetRect();
+  if (lastTextFrame->GetWritingMode().IsVertical()) {
+    // Below of the last text frame.
+    result.mRect.SetRect(0, kLastTextFrameRect.height,
+                         kLastTextFrameRect.width, 0);
+  } else {
+    // Right of the last text frame (not bidi-aware).
+    result.mRect.SetRect(kLastTextFrameRect.width, 0,
+                         0, kLastTextFrameRect.height);
+  }
+  result.mBaseFrame = lastTextFrame;
+  return result;
+}
+
+ContentEventHandler::FrameRelativeRect
+ContentEventHandler::GuessFirstCaretRectIn(nsIFrame* aFrame)
+{
+  const WritingMode kWritingMode = aFrame->GetWritingMode();
+
+  // Computes the font height, but if it's not available, we should use
+  // default font size of Firefox.  The default font size in default settings
+  // is 16px.
+  RefPtr<nsFontMetrics> fontMetrics =
+    nsLayoutUtils::GetInflatedFontMetricsForFrame(aFrame);
+  const nscoord kMaxHeight =
+    fontMetrics ? fontMetrics->MaxHeight() :
+                  16 * mPresContext->AppUnitsPerDevPixel();
+
+  nsRect caretRect;
+  const nsRect kContentRect = aFrame->GetContentRect() - aFrame->GetPosition();
+  caretRect.y = kContentRect.y;
+  if (!kWritingMode.IsVertical()) {
+    if (kWritingMode.IsBidiLTR()) {
+      caretRect.x = kContentRect.x;
+    } else {
+      // Move 1px left for the space of caret itself.
+      const nscoord kOnePixel = mPresContext->AppUnitsPerDevPixel();
+      caretRect.x = kContentRect.XMost() - kOnePixel;
+    }
+    caretRect.height = kMaxHeight;
+    // However, don't add kOnePixel here because it may cause 2px width at
+    // aligning the edge to device pixels.
+    caretRect.width = 1;
+  } else {
+    if (kWritingMode.IsVerticalLR()) {
+      caretRect.x = kContentRect.x;
+    } else {
+      caretRect.x = kContentRect.XMost() - kMaxHeight;
+    }
+    caretRect.width = kMaxHeight;
+    // Don't add app units for a device pixel because it may cause 2px height
+    // at aligning the edge to device pixels.
+    caretRect.height = 1;
+  }
+  return FrameRelativeRect(caretRect, aFrame);
+}
+
+nsresult
+ContentEventHandler::OnQueryTextRectArray(WidgetQueryContentEvent* aEvent)
+{
+  nsresult rv = Init(aEvent);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  LineBreakType lineBreakType = GetLineBreakType(aEvent);
+  const uint32_t kBRLength = GetBRLength(lineBreakType);
+
+  RefPtr<nsRange> range = new nsRange(mRootContent);
+
+  bool isVertical = false;
+  LayoutDeviceIntRect rect;
+  uint32_t offset = aEvent->mInput.mOffset;
+  const uint32_t kEndOffset = offset + aEvent->mInput.mLength;
+  bool wasLineBreaker = false;
+  // lastCharRect stores the last charRect value (see below for the detail of
+  // charRect).
+  nsRect lastCharRect;
+  // lastFrame is base frame of lastCharRect.
+  nsIFrame* lastFrame = nullptr;
+  while (offset < kEndOffset) {
+    nsCOMPtr<nsIContent> lastTextContent;
+    rv = SetRangeFromFlatTextOffset(range, offset, 1, lineBreakType, true,
+                                    nullptr, getter_AddRefs(lastTextContent));
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return rv;
+    }
+
+    // If the range is collapsed, offset has already reached the end of the
+    // contents.
+    if (range->Collapsed()) {
+      break;
+    }
+
+    // Get the first frame which causes some text after the offset.
+    FrameAndNodeOffset firstFrame = GetFirstFrameInRangeForTextRect(range);
+
+    // If GetFirstFrameInRangeForTextRect() does not return valid frame, that
+    // means that there are no visible frames having text or the offset reached
+    // the end of contents.
+    if (!firstFrame.IsValid()) {
+      nsAutoString allText;
+      rv = GenerateFlatTextContent(mRootContent, allText, lineBreakType);
+      // If the offset doesn't reach the end of contents yet but there is no
+      // frames for the node, that means that current offset's node is hidden
+      // by CSS or something.  Ideally, we should handle it with the last
+      // visible text node's last character's rect, but it's not usual cases
+      // in actual web services.  Therefore, currently, we should make this
+      // case fail.
+      if (NS_WARN_IF(NS_FAILED(rv)) || offset < allText.Length()) {
+        return NS_ERROR_FAILURE;
+      }
+      // Otherwise, we should append caret rect at the end of the contents
+      // later.
+      break;
+    }
+
+    nsIContent* firstContent = firstFrame.mFrame->GetContent();
+    if (NS_WARN_IF(!firstContent)) {
+      return NS_ERROR_FAILURE;
+    }
+
+    bool startsBetweenLineBreaker = false;
+    nsAutoString chars;
+    // XXX not bidi-aware this class...
+    isVertical = firstFrame->GetWritingMode().IsVertical();
+
+    nsIFrame* baseFrame = firstFrame;
+    // charRect should have each character rect or line breaker rect relative
+    // to the base frame.
+    AutoTArray<nsRect, 16> charRects;
+
+    // If the first frame is a text frame, the result should be computed with
+    // the frame's API.
+    if (firstFrame->GetType() == nsGkAtoms::textFrame) {
+      rv = firstFrame->GetCharacterRectsInRange(firstFrame.mOffsetInNode,
+                                                kEndOffset - offset, charRects);
+      if (NS_WARN_IF(NS_FAILED(rv)) || NS_WARN_IF(charRects.IsEmpty())) {
+        return rv;
+      }
+      // Assign the characters whose rects are computed by the call of
+      // nsTextFrame::GetCharacterRectsInRange().
+      AppendSubString(chars, firstContent, firstFrame.mOffsetInNode,
+                      charRects.Length());
+      if (NS_WARN_IF(chars.Length() != charRects.Length())) {
+        return NS_ERROR_UNEXPECTED;
+      }
+      if (kBRLength > 1 && chars[0] == '\n' &&
+          offset == aEvent->mInput.mOffset && offset) {
+        // If start of range starting from previous offset of query range is
+        // same as the start of query range, the query range starts from
+        // between a line breaker (i.e., the range starts between "\r" and
+        // "\n").
+        RefPtr<nsRange> rangeToPrevOffset = new nsRange(mRootContent);
+        rv = SetRangeFromFlatTextOffset(rangeToPrevOffset,
+                                        aEvent->mInput.mOffset - 1, 1,
+                                        lineBreakType, true, nullptr);
+        if (NS_WARN_IF(NS_FAILED(rv))) {
+          return rv;
+        }
+        startsBetweenLineBreaker =
+          range->GetStartParent() == rangeToPrevOffset->GetStartParent() &&
+          range->StartOffset() == rangeToPrevOffset->StartOffset();
+      }
+    }
+    // Other contents should cause a line breaker rect before it.
+    // Note that moz-<br> element does not cause any text, however,
+    // it represents empty line at the last of current block.  Therefore,
+    // we need to compute its rect too.
+    else if (ShouldBreakLineBefore(firstContent, mRootContent) ||
+             IsMozBR(firstContent)) {
+      nsRect brRect;
+      // If the frame is not a <br> frame, we need to compute the caret rect
+      // with last character's rect before firstContent if there is.
+      // For example, if caret is after "c" of |<p>abc</p><p>def</p>|, IME may
+      // query a line breaker's rect after "c".  Then, if we compute it only
+      // with the 2nd <p>'s block frame, the result will be:
+      //  +-<p>--------------------------------+
+      //  |abc                                 |
+      //  +------------------------------------+
+      //
+      // I+-<p>--------------------------------+
+      //  |def                                 |
+      //  +------------------------------------+
+      // However, users expect popup windows of IME should be positioned at
+      // right-bottom of "c" like this:
+      //  +-<p>--------------------------------+
+      //  |abcI                                |
+      //  +------------------------------------+
+      //
+      //  +-<p>--------------------------------+
+      //  |def                                 |
+      //  +------------------------------------+
+      // Therefore, if the first frame isn't a <br> frame and there is a text
+      // node before the first node in the queried range, we should compute the
+      // first rect with the previous character's rect.
+      // If we already compute a character's rect in the queried range, we can
+      // compute it with the cached last character's rect.  (However, don't
+      // use this path if it's a <br> frame because trusting <br> frame's rect
+      // is better than guessing the rect from the previous character.)
+      if (firstFrame->GetType() != nsGkAtoms::brFrame &&
+          aEvent->mInput.mOffset != offset) {
+        baseFrame = lastFrame;
+        brRect = lastCharRect;
+        if (!wasLineBreaker) {
+          if (isVertical) {
+            // Right of the last character.
+            brRect.y = brRect.YMost() + 1;
+            brRect.height = 1;
+          } else {
+            // Under the last character.
+            brRect.x = brRect.XMost() + 1;
+            brRect.width = 1;
+          }
+        }
+      }
+      // If it's not a <br> frame and it's the first character rect at the
+      // queried range, we need to the previous character of the start of
+      // the queried range if there is a text node.
+      else if (firstFrame->GetType() != nsGkAtoms::brFrame && lastTextContent) {
+        FrameRelativeRect brRectRelativeToLastTextFrame =
+          GuessLineBreakerRectAfter(lastTextContent);
+        if (NS_WARN_IF(!brRectRelativeToLastTextFrame.IsValid())) {
+          return NS_ERROR_FAILURE;
+        }
+        // Look for the last text frame for lastTextContent.
+        nsIFrame* primaryFrame = lastTextContent->GetPrimaryFrame();
+        if (NS_WARN_IF(!primaryFrame)) {
+          return NS_ERROR_FAILURE;
+        }
+        baseFrame = primaryFrame->LastContinuation();
+        if (NS_WARN_IF(!baseFrame)) {
+          return NS_ERROR_FAILURE;
+        }
+        brRect = brRectRelativeToLastTextFrame.RectRelativeTo(baseFrame);
+      }
+      // Otherwise, we need to compute the line breaker's rect only with the
+      // first frame's rect.  But this may be unexpected.  For example,
+      // |<div contenteditable>[<p>]abc</p></div>|.  In this case, caret is
+      // before "a", therefore, users expect the rect left of "a".  However,
+      // we don't have enough information about the next character here and
+      // this isn't usual case (e.g., IME typically tries to query the rect
+      // of "a" or caret rect for computing its popup position).  Therefore,
+      // we shouldn't do more complicated hack here unless we'll get some bug
+      // reports actually.
+      else {
+        FrameRelativeRect relativeBRRect = GetLineBreakerRectBefore(firstFrame);
+        brRect = relativeBRRect.RectRelativeTo(firstFrame);
+      }
+      charRects.AppendElement(brRect);
+      chars.AssignLiteral("\n");
+      if (kBRLength > 1 && offset == aEvent->mInput.mOffset && offset) {
+        // If the first frame for the previous offset of the query range and
+        // the first frame for the start of query range are same, that means
+        // the start offset is between the first line breaker (i.e., the range
+        // starts between "\r" and "\n").
+        rv = SetRangeFromFlatTextOffset(range, aEvent->mInput.mOffset - 1, 1,
+                                        lineBreakType, true, nullptr);
+        if (NS_WARN_IF(NS_FAILED(rv))) {
+          return NS_ERROR_UNEXPECTED;
+        }
+        FrameAndNodeOffset frameForPrevious =
+          GetFirstFrameInRangeForTextRect(range);
+        startsBetweenLineBreaker = frameForPrevious.mFrame == firstFrame.mFrame;
+      }
+    } else {
+      NS_WARNING("The frame is neither a text frame nor a frame whose content "
+                 "causes a line break");
+      return NS_ERROR_FAILURE;
+    }
+
+    for (size_t i = 0; i < charRects.Length() && offset < kEndOffset; i++) {
+      nsRect charRect = charRects[i];
+      // Store lastCharRect before applying CSS transform because it may be
+      // used for computing a line breaker rect.  Then, the computed line
+      // breaker rect will be applied CSS transform again.  Therefore,
+      // the value of lastCharRect should be raw rect value relative to the
+      // base frame.
+      lastCharRect = charRect;
+      lastFrame = baseFrame;
+      rv = ConvertToRootRelativeOffset(baseFrame, charRect);
+      if (NS_WARN_IF(NS_FAILED(rv))) {
+        return rv;
+      }
+
+      rect = LayoutDeviceIntRect::FromUnknownRect(
+               charRect.ToOutsidePixels(mPresContext->AppUnitsPerDevPixel()));
+      // Returning empty rect may cause native IME confused, let's make sure to
+      // return non-empty rect.
+      EnsureNonEmptyRect(rect);
+
+      aEvent->mReply.mRectArray.AppendElement(rect);
+      offset++;
+
+      // If it's not a line breaker or the line breaker length is same as
+      // XP line breaker's, we need to do nothing for current character.
+      wasLineBreaker = chars[i] == '\n';
+      if (!wasLineBreaker || kBRLength == 1) {
+        continue;
+      }
+
+      MOZ_ASSERT(kBRLength == 2);
+
+      // If it's already reached the end of query range, we don't need to do
+      // anymore.
+      if (offset == kEndOffset) {
+        break;
+      }
+
+      // If the query range starts from between a line breaker, i.e., it starts
+      // between "\r" and "\n", the appended rect was for the "\n".  Therefore,
+      // we don't need to append same rect anymore for current "\r\n".
+      if (startsBetweenLineBreaker) {
+        continue;
+      }
+
+      // The appended rect was for "\r" of "\r\n".  Therefore, we need to
+      // append same rect for "\n" too because querying rect of "\r" and "\n"
+      // should return same rect.  E.g., IME may query previous character's
+      // rect of first character of a line.
+      aEvent->mReply.mRectArray.AppendElement(rect);
+      offset++;
+    }
+  }
+
+  // If the query range is longer than actual content length, we should append
+  // caret rect at the end of the content as the last character rect because
+  // native IME may want to query character rect at the end of contents for
+  // deciding the position of a popup window (e.g., suggest window for next
+  // word).  Note that when this method hasn't appended character rects, it
+  // means that the offset is too large or the query range is collapsed.
+  if (offset < kEndOffset || aEvent->mReply.mRectArray.IsEmpty()) {
+    // If we've already retrieved some character rects before current offset,
+    // we can guess the last rect from the last character's rect unless it's a
+    // line breaker.  (If it's a line breaker, the caret rect is in next line.)
+    if (!aEvent->mReply.mRectArray.IsEmpty() && !wasLineBreaker) {
+      rect = aEvent->mReply.mRectArray.LastElement();
+      if (isVertical) {
+        rect.y = rect.YMost() + 1;
+        rect.height = 1;
+        MOZ_ASSERT(rect.width);
+      } else {
+        rect.x = rect.XMost() + 1;
+        rect.width = 1;
+        MOZ_ASSERT(rect.height);
+      }
+      aEvent->mReply.mRectArray.AppendElement(rect);
+    } else {
+      // Note that don't use eQueryCaretRect here because if caret is at the
+      // end of the content, it returns actual caret rect instead of computing
+      // the rect itself.  It means that the result depends on caret position.
+      // So, we shouldn't use it for consistency result in automated tests.
+      WidgetQueryContentEvent queryTextRect(eQueryTextRect, *aEvent);
+      WidgetQueryContentEvent::Options options(*aEvent);
+      queryTextRect.InitForQueryTextRect(offset, 1, options);
+      rv = OnQueryTextRect(&queryTextRect);
+      if (NS_WARN_IF(NS_FAILED(rv))) {
+        return rv;
+      }
+      if (NS_WARN_IF(!queryTextRect.mSucceeded)) {
+        return NS_ERROR_FAILURE;
+      }
+      MOZ_ASSERT(!queryTextRect.mReply.mRect.IsEmpty());
+      if (queryTextRect.mReply.mWritingMode.IsVertical()) {
+        queryTextRect.mReply.mRect.height = 1;
+      } else {
+        queryTextRect.mReply.mRect.width = 1;
+      }
+      aEvent->mReply.mRectArray.AppendElement(queryTextRect.mReply.mRect);
+    }
+  }
+
+  aEvent->mSucceeded = true;
+  return NS_OK;
+}
+
+nsresult
+ContentEventHandler::OnQueryTextRect(WidgetQueryContentEvent* aEvent)
+{
+  nsresult rv = Init(aEvent);
+  if (NS_FAILED(rv)) {
+    return rv;
+  }
+
+  // If mLength is 0 (this may be caused by bug of native IME), we should
+  // redirect this event to OnQueryCaretRect().
+  if (!aEvent->mInput.mLength) {
+    return OnQueryCaretRect(aEvent);
+  }
+
+  LineBreakType lineBreakType = GetLineBreakType(aEvent);
+  RefPtr<nsRange> range = new nsRange(mRootContent);
+  nsCOMPtr<nsIContent> lastTextContent;
+  rv = SetRangeFromFlatTextOffset(range, aEvent->mInput.mOffset,
+                                  aEvent->mInput.mLength, lineBreakType, true,
+                                  &aEvent->mReply.mOffset,
+                                  getter_AddRefs(lastTextContent));
+  NS_ENSURE_SUCCESS(rv, rv);
+  rv = GenerateFlatTextContent(range, aEvent->mReply.mString, lineBreakType);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  // used to iterate over all contents and their frames
+  nsCOMPtr<nsIContentIterator> iter = NS_NewContentIterator();
+  iter->Init(range);
+
+  // Get the first frame which causes some text after the offset.
+  FrameAndNodeOffset firstFrame = GetFirstFrameInRangeForTextRect(range);
+
+  // If GetFirstFrameInRangeForTextRect() does not return valid frame, that
+  // means that there are no visible frames having text or the offset reached
+  // the end of contents.
+  if (!firstFrame.IsValid()) {
+    nsAutoString allText;
+    rv = GenerateFlatTextContent(mRootContent, allText, lineBreakType);
+    // If the offset doesn't reach the end of contents but there is no frames
+    // for the node, that means that current offset's node is hidden by CSS or
+    // something.  Ideally, we should handle it with the last visible text
+    // node's last character's rect, but it's not usual cases in actual web
+    // services.  Therefore, currently, we should make this case fail.
+    if (NS_WARN_IF(NS_FAILED(rv)) ||
+        static_cast<uint32_t>(aEvent->mInput.mOffset) < allText.Length()) {
+      return NS_ERROR_FAILURE;
+    }
+
+    // Look for the last frame which should be included text rects.
+    ErrorResult erv;
+    range->SelectNodeContents(*mRootContent, erv);
+    if (NS_WARN_IF(erv.Failed())) {
+      return NS_ERROR_UNEXPECTED;
+    }
+    nsRect rect;
+    FrameAndNodeOffset lastFrame = GetLastFrameInRangeForTextRect(range);
+    // If there is at least one frame which can be used for computing a rect
+    // for a character or a line breaker, we should use it for guessing the
+    // caret rect at the end of the contents.
+    if (lastFrame) {
+      if (NS_WARN_IF(!lastFrame->GetContent())) {
+        return NS_ERROR_FAILURE;
+      }
+      FrameRelativeRect relativeRect;
+      // If there is a <br> frame at the end, it represents an empty line at
+      // the end with moz-<br> or content <br> in a block level element.
+      if (lastFrame->GetType() == nsGkAtoms::brFrame) {
+        relativeRect = GetLineBreakerRectBefore(lastFrame);
+      }
+      // If there is a text frame at the end, use its information.
+      else if (lastFrame->GetType() == nsGkAtoms::textFrame) {
+        relativeRect = GuessLineBreakerRectAfter(lastFrame->GetContent());
+      }
+      // If there is an empty frame which is neither a text frame nor a <br>
+      // frame at the end, guess caret rect in it.
+      else {
+        relativeRect = GuessFirstCaretRectIn(lastFrame);
+      }
+      if (NS_WARN_IF(!relativeRect.IsValid())) {
+        return NS_ERROR_FAILURE;
+      }
+      rect = relativeRect.RectRelativeTo(lastFrame);
+      rv = ConvertToRootRelativeOffset(lastFrame, rect);
+      if (NS_WARN_IF(NS_FAILED(rv))) {
+        return rv;
+      }
+      aEvent->mReply.mWritingMode = lastFrame->GetWritingMode();
+    }
+    // Otherwise, if there are no contents in mRootContent, guess caret rect in
+    // its frame (with its font height and content box).
+    else {
+      nsIFrame* rootContentFrame = mRootContent->GetPrimaryFrame();
+      if (NS_WARN_IF(!rootContentFrame)) {
+        return NS_ERROR_FAILURE;
+      }
+      FrameRelativeRect relativeRect = GuessFirstCaretRectIn(rootContentFrame);
+      if (NS_WARN_IF(!relativeRect.IsValid())) {
+        return NS_ERROR_FAILURE;
+      }
+      rect = relativeRect.RectRelativeTo(rootContentFrame);
+      rv = ConvertToRootRelativeOffset(rootContentFrame, rect);
+      if (NS_WARN_IF(NS_FAILED(rv))) {
+        return rv;
+      }
+      aEvent->mReply.mWritingMode = rootContentFrame->GetWritingMode();
+    }
+    aEvent->mReply.mRect = LayoutDeviceIntRect::FromUnknownRect(
+      rect.ToOutsidePixels(mPresContext->AppUnitsPerDevPixel()));
+    EnsureNonEmptyRect(aEvent->mReply.mRect);
+    aEvent->mSucceeded = true;
+    return NS_OK;
+  }
+
+  nsRect rect, frameRect;
+  nsPoint ptOffset;
+
+  // If the first frame is a text frame, the result should be computed with
+  // the frame's rect but not including the rect before start point of the
+  // queried range.
+  if (firstFrame->GetType() == nsGkAtoms::textFrame) {
+    rect.SetRect(nsPoint(0, 0), firstFrame->GetRect().Size());
+    rv = ConvertToRootRelativeOffset(firstFrame, rect);
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return rv;
+    }
+    frameRect = rect;
+    // Exclude the rect before start point of the queried range.
+    firstFrame->GetPointFromOffset(firstFrame.mOffsetInNode, &ptOffset);
+    if (firstFrame->GetWritingMode().IsVertical()) {
+      rect.y += ptOffset.y;
+      rect.height -= ptOffset.y;
+    } else {
+      rect.x += ptOffset.x;
+      rect.width -= ptOffset.x;
+    }
+  }
+  // If first frame causes a line breaker but it's not a <br> frame, we cannot
+  // compute proper rect only with the frame because typically caret is at
+  // right of the last character of it.  For example, if caret is after "c" of
+  // |<p>abc</p><p>def</p>|, IME may query a line breaker's rect after "c".
+  // Then, if we compute it only with the 2nd <p>'s block frame, the result
+  // will be:
+  //  +-<p>--------------------------------+
+  //  |abc                                 |
+  //  +------------------------------------+
+  //
+  // I+-<p>--------------------------------+
+  //  |def                                 |
+  //  +------------------------------------+
+  // However, users expect popup windows of IME should be positioned at
+  // right-bottom of "c" like this:
+  //  +-<p>--------------------------------+
+  //  |abcI                                |
+  //  +------------------------------------+
+  //
+  //  +-<p>--------------------------------+
+  //  |def                                 |
+  //  +------------------------------------+
+  // Therefore, if the first frame isn't a <br> frame and there is a text
+  // node before the first node in the queried range, we should compute the
+  // first rect with the previous character's rect.
+  else if (firstFrame->GetType() != nsGkAtoms::brFrame && lastTextContent) {
+    FrameRelativeRect brRectAfterLastChar =
+      GuessLineBreakerRectAfter(lastTextContent);
+    if (NS_WARN_IF(!brRectAfterLastChar.IsValid())) {
+      return NS_ERROR_FAILURE;
+    }
+    rect = brRectAfterLastChar.mRect;
+    rv = ConvertToRootRelativeOffset(brRectAfterLastChar.mBaseFrame, rect);
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return rv;
+    }
+    frameRect = rect;
+  }
+  // Otherwise, we need to compute the line breaker's rect only with the
+  // first frame's rect.  But this may be unexpected.  For example,
+  // |<div contenteditable>[<p>]abc</p></div>|.  In this case, caret is before
+  // "a", therefore, users expect the rect left of "a".  However, we don't
+  // have enough information about the next character here and this isn't
+  // usual case (e.g., IME typically tries to query the rect of "a" or caret
+  // rect for computing its popup position).  Therefore, we shouldn't do
+  // more complicated hack here unless we'll get some bug reports actually.
+  else {
+    FrameRelativeRect relativeRect = GetLineBreakerRectBefore(firstFrame);
+    if (NS_WARN_IF(!relativeRect.IsValid())) {
+      return NS_ERROR_FAILURE;
+    }
+    rect = relativeRect.RectRelativeTo(firstFrame);
+    rv = ConvertToRootRelativeOffset(firstFrame, rect);
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return rv;
+    }
+    frameRect = rect;
+  }
+  // UnionRect() requires non-empty rect.  So, let's make sure to get non-emtpy
+  // rect from the first frame.
+  EnsureNonEmptyRect(rect);
+
+  // Get the last frame which causes some text in the range.
+  FrameAndNodeOffset lastFrame = GetLastFrameInRangeForTextRect(range);
+  if (NS_WARN_IF(!lastFrame.IsValid())) {
+    return NS_ERROR_FAILURE;
+  }
+
+  // iterate over all covered frames
+  for (nsIFrame* frame = firstFrame; frame != lastFrame;) {
+    frame = frame->GetNextContinuation();
+    if (!frame) {
+      do {
+        iter->Next();
+        nsINode* node = iter->GetCurrentNode();
+        if (!node) {
+          break;
+        }
+        if (!node->IsNodeOfType(nsINode::eCONTENT)) {
+          continue;
+        }
+        nsIFrame* primaryFrame = node->AsContent()->GetPrimaryFrame();
+        // The node may be hidden by CSS.
+        if (!primaryFrame) {
+          continue;
+        }
+        // We should take only text frame's rect and br frame's rect.  We can
+        // always use frame rect of text frame and GetLineBreakerRectBefore()
+        // can return exactly correct rect only for <br> frame for now.  On the
+        // other hand, GetLineBreakRectBefore() returns guessed caret rect for
+        // the other frames.  We shouldn't include such odd rect to the result.
+        if (primaryFrame->GetType() == nsGkAtoms::textFrame ||
+            primaryFrame->GetType() == nsGkAtoms::brFrame) {
+          frame = primaryFrame;
+        }
+      } while (!frame && !iter->IsDone());
+      if (!frame) {
+        break;
+      }
+    }
+    if (frame->GetType() == nsGkAtoms::textFrame) {
+      frameRect.SetRect(nsPoint(0, 0), frame->GetRect().Size());
+    } else {
+      MOZ_ASSERT(frame->GetType() == nsGkAtoms::brFrame);
+      FrameRelativeRect relativeRect = GetLineBreakerRectBefore(frame);
+      if (NS_WARN_IF(!relativeRect.IsValid())) {
+        return NS_ERROR_FAILURE;
+      }
+      frameRect = relativeRect.RectRelativeTo(frame);
+    }
+    rv = ConvertToRootRelativeOffset(frame, frameRect);
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return rv;
+    }
+    // UnionRect() requires non-empty rect.  So, let's make sure to get
+    // non-emtpy rect from the frame.
+    EnsureNonEmptyRect(frameRect);
+    if (frame != lastFrame) {
+      // not last frame, so just add rect to previous result
+      rect.UnionRect(rect, frameRect);
+    }
+  }
+
+  // Get the ending frame rect.
+  // FYI: If first frame and last frame are same, frameRect is already set
+  //      to the rect excluding the text before the query range.
+  if (firstFrame.mFrame != lastFrame.mFrame) {
+    frameRect.SetRect(nsPoint(0, 0), lastFrame->GetRect().Size());
+    rv = ConvertToRootRelativeOffset(lastFrame, frameRect);
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return rv;
+    }
+  }
+
+  // Shrink the last frame for cutting off the text after the query range.
+  if (lastFrame->GetType() == nsGkAtoms::textFrame) {
+    lastFrame->GetPointFromOffset(lastFrame.mOffsetInNode, &ptOffset);
+    if (lastFrame->GetWritingMode().IsVertical()) {
+      frameRect.height -= lastFrame->GetRect().height - ptOffset.y;
+    } else {
+      frameRect.width -= lastFrame->GetRect().width - ptOffset.x;
+    }
+    // UnionRect() requires non-empty rect.  So, let's make sure to get
+    // non-empty rect from the last frame.
+    EnsureNonEmptyRect(frameRect);
+
+    if (firstFrame.mFrame == lastFrame.mFrame) {
+      rect.IntersectRect(rect, frameRect);
+    } else {
+      rect.UnionRect(rect, frameRect);
+    }
+  }
+
+  aEvent->mReply.mRect = LayoutDeviceIntRect::FromUnknownRect(
+      rect.ToOutsidePixels(mPresContext->AppUnitsPerDevPixel()));
+  // Returning empty rect may cause native IME confused, let's make sure to
+  // return non-empty rect.
+  EnsureNonEmptyRect(aEvent->mReply.mRect);
+  aEvent->mReply.mWritingMode = lastFrame->GetWritingMode();
+  aEvent->mSucceeded = true;
+  return NS_OK;
+}
+
+nsresult
+ContentEventHandler::OnQueryEditorRect(WidgetQueryContentEvent* aEvent)
+{
+  nsresult rv = Init(aEvent);
+  if (NS_FAILED(rv)) {
+    return rv;
+  }
+
+  nsIContent* focusedContent = GetFocusedContent();
+  rv = QueryContentRect(IsPlugin(focusedContent) ?
+                          focusedContent : mRootContent.get(), aEvent);
+  NS_ENSURE_SUCCESS(rv, rv);
+  return NS_OK;
+}
+
+nsresult
+ContentEventHandler::OnQueryCaretRect(WidgetQueryContentEvent* aEvent)
+{
+  nsresult rv = Init(aEvent);
+  if (NS_FAILED(rv)) {
+    return rv;
+  }
+
+  // When the selection is collapsed and the queried offset is current caret
+  // position, we should return the "real" caret rect.
+  if (mSelection->IsCollapsed()) {
+    nsRect caretRect;
+    nsIFrame* caretFrame = nsCaret::GetGeometry(mSelection, &caretRect);
+    if (caretFrame) {
+      uint32_t offset;
+      rv = GetStartOffset(mFirstSelectedRange,
+                          &offset, GetLineBreakType(aEvent));
+      NS_ENSURE_SUCCESS(rv, rv);
+      if (offset == aEvent->mInput.mOffset) {
+        rv = ConvertToRootRelativeOffset(caretFrame, caretRect);
+        NS_ENSURE_SUCCESS(rv, rv);
+        nscoord appUnitsPerDevPixel =
+          caretFrame->PresContext()->AppUnitsPerDevPixel();
+        aEvent->mReply.mRect = LayoutDeviceIntRect::FromUnknownRect(
+          caretRect.ToOutsidePixels(appUnitsPerDevPixel));
+        // Returning empty rect may cause native IME confused, let's make sure
+        // to return non-empty rect.
+        EnsureNonEmptyRect(aEvent->mReply.mRect);
+        aEvent->mReply.mWritingMode = caretFrame->GetWritingMode();
+        aEvent->mReply.mOffset = aEvent->mInput.mOffset;
+        aEvent->mSucceeded = true;
+        return NS_OK;
+      }
+    }
+  }
+
+  // Otherwise, we should guess the caret rect from the character's rect.
+  WidgetQueryContentEvent queryTextRectEvent(eQueryTextRect, *aEvent);
+  WidgetQueryContentEvent::Options options(*aEvent);
+  queryTextRectEvent.InitForQueryTextRect(aEvent->mInput.mOffset, 1, options);
+  rv = OnQueryTextRect(&queryTextRectEvent);
+  if (NS_WARN_IF(NS_FAILED(rv)) || NS_WARN_IF(!queryTextRectEvent.mSucceeded)) {
+    return NS_ERROR_FAILURE;
+  }
+  queryTextRectEvent.mReply.mString.Truncate();
+  aEvent->mReply = queryTextRectEvent.mReply;
+  if (aEvent->GetWritingMode().IsVertical()) {
+    aEvent->mReply.mRect.height = 1;
+  } else {
+    aEvent->mReply.mRect.width = 1;
+  }
+  // Returning empty rect may cause native IME confused, let's make sure to
+  // return non-empty rect.
+  aEvent->mSucceeded = true;
+  return NS_OK;
+}
+
+nsresult
+ContentEventHandler::OnQueryContentState(WidgetQueryContentEvent* aEvent)
+{
+  nsresult rv = Init(aEvent);
+  if (NS_FAILED(rv)) {
+    return rv;
+  }
+  aEvent->mSucceeded = true;
+  return NS_OK;
+}
+
+nsresult
+ContentEventHandler::OnQuerySelectionAsTransferable(
+                       WidgetQueryContentEvent* aEvent)
+{
+  nsresult rv = Init(aEvent);
+  if (NS_FAILED(rv)) {
+    return rv;
+  }
+
+  if (!aEvent->mReply.mHasSelection) {
+    aEvent->mSucceeded = true;
+    aEvent->mReply.mTransferable = nullptr;
+    return NS_OK;
+  }
+
+  nsCOMPtr<nsIDocument> doc = mPresShell->GetDocument();
+  NS_ENSURE_TRUE(doc, NS_ERROR_FAILURE);
+
+  rv = nsCopySupport::GetTransferableForSelection(
+         mSelection, doc, getter_AddRefs(aEvent->mReply.mTransferable));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  aEvent->mSucceeded = true;
+  return NS_OK;
+}
+
+nsresult
+ContentEventHandler::OnQueryCharacterAtPoint(WidgetQueryContentEvent* aEvent)
+{
+  nsresult rv = Init(aEvent);
+  if (NS_FAILED(rv)) {
+    return rv;
+  }
+
+  aEvent->mReply.mOffset = aEvent->mReply.mTentativeCaretOffset =
+    WidgetQueryContentEvent::NOT_FOUND;
+
+  nsIFrame* rootFrame = mPresShell->GetRootFrame();
+  NS_ENSURE_TRUE(rootFrame, NS_ERROR_FAILURE);
+  nsIWidget* rootWidget = rootFrame->GetNearestWidget();
+  NS_ENSURE_TRUE(rootWidget, NS_ERROR_FAILURE);
+
+  // The root frame's widget might be different, e.g., the event was fired on
+  // a popup but the rootFrame is the document root.
+  if (rootWidget != aEvent->mWidget) {
+    NS_PRECONDITION(aEvent->mWidget, "The event must have the widget");
+    nsView* view = nsView::GetViewFor(aEvent->mWidget);
+    NS_ENSURE_TRUE(view, NS_ERROR_FAILURE);
+    rootFrame = view->GetFrame();
+    NS_ENSURE_TRUE(rootFrame, NS_ERROR_FAILURE);
+    rootWidget = rootFrame->GetNearestWidget();
+    NS_ENSURE_TRUE(rootWidget, NS_ERROR_FAILURE);
+  }
+
+  WidgetQueryContentEvent eventOnRoot(true, eQueryCharacterAtPoint,
+                                      rootWidget);
+  eventOnRoot.mUseNativeLineBreak = aEvent->mUseNativeLineBreak;
+  eventOnRoot.mRefPoint = aEvent->mRefPoint;
+  if (rootWidget != aEvent->mWidget) {
+    eventOnRoot.mRefPoint += aEvent->mWidget->WidgetToScreenOffset() -
+      rootWidget->WidgetToScreenOffset();
+  }
+  nsPoint ptInRoot =
+    nsLayoutUtils::GetEventCoordinatesRelativeTo(&eventOnRoot, rootFrame);
+
+  nsIFrame* targetFrame = nsLayoutUtils::GetFrameForPoint(rootFrame, ptInRoot);
+  if (!targetFrame || !targetFrame->GetContent() ||
+      !nsContentUtils::ContentIsDescendantOf(targetFrame->GetContent(),
+                                             mRootContent)) {
+    // There is no character at the point.
+    aEvent->mSucceeded = true;
+    return NS_OK;
+  }
+  nsPoint ptInTarget = ptInRoot + rootFrame->GetOffsetToCrossDoc(targetFrame);
+  int32_t rootAPD = rootFrame->PresContext()->AppUnitsPerDevPixel();
+  int32_t targetAPD = targetFrame->PresContext()->AppUnitsPerDevPixel();
+  ptInTarget = ptInTarget.ScaleToOtherAppUnits(rootAPD, targetAPD);
+
+  nsIFrame::ContentOffsets tentativeCaretOffsets =
+    targetFrame->GetContentOffsetsFromPoint(ptInTarget);
+  if (!tentativeCaretOffsets.content ||
+      !nsContentUtils::ContentIsDescendantOf(tentativeCaretOffsets.content,
+                                             mRootContent)) {
+    // There is no character nor tentative caret point at the point.
+    aEvent->mSucceeded = true;
+    return NS_OK;
+  }
+
+  rv = GetFlatTextLengthInRange(NodePosition(mRootContent, 0),
+                                NodePosition(tentativeCaretOffsets),
+                                mRootContent,
+                                &aEvent->mReply.mTentativeCaretOffset,
+                                GetLineBreakType(aEvent));
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  if (targetFrame->GetType() != nsGkAtoms::textFrame) {
+    // There is no character at the point but there is tentative caret point.
+    aEvent->mSucceeded = true;
+    return NS_OK;
+  }
+
+  MOZ_ASSERT(
+    aEvent->mReply.mTentativeCaretOffset != WidgetQueryContentEvent::NOT_FOUND,
+    "The point is inside a character bounding box.  Why tentative caret point "
+    "hasn't been found?");
+
+  nsTextFrame* textframe = static_cast<nsTextFrame*>(targetFrame);
+  nsIFrame::ContentOffsets contentOffsets =
+    textframe->GetCharacterOffsetAtFramePoint(ptInTarget);
+  NS_ENSURE_TRUE(contentOffsets.content, NS_ERROR_FAILURE);
+  uint32_t offset;
+  rv = GetFlatTextLengthInRange(NodePosition(mRootContent, 0),
+                                NodePosition(contentOffsets),
+                                mRootContent, &offset,
+                                GetLineBreakType(aEvent));
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  WidgetQueryContentEvent textRect(true, eQueryTextRect, aEvent->mWidget);
+  WidgetQueryContentEvent::Options options(*aEvent);
+  textRect.InitForQueryTextRect(offset, 1, options);
+  rv = OnQueryTextRect(&textRect);
+  NS_ENSURE_SUCCESS(rv, rv);
+  NS_ENSURE_TRUE(textRect.mSucceeded, NS_ERROR_FAILURE);
+
+  // currently, we don't need to get the actual text.
+  aEvent->mReply.mOffset = offset;
+  aEvent->mReply.mRect = textRect.mReply.mRect;
+  aEvent->mSucceeded = true;
+  return NS_OK;
+}
+
+nsresult
+ContentEventHandler::OnQueryDOMWidgetHittest(WidgetQueryContentEvent* aEvent)
+{
+  NS_ASSERTION(aEvent, "aEvent must not be null");
+
+  nsresult rv = InitBasic();
+  if (NS_FAILED(rv)) {
+    return rv;
+  }
+
+  aEvent->mSucceeded = false;
+  aEvent->mReply.mWidgetIsHit = false;
+
+  NS_ENSURE_TRUE(aEvent->mWidget, NS_ERROR_FAILURE);
+
+  nsIDocument* doc = mPresShell->GetDocument();
+  NS_ENSURE_TRUE(doc, NS_ERROR_FAILURE);
+  nsIFrame* docFrame = mPresShell->GetRootFrame();
+  NS_ENSURE_TRUE(docFrame, NS_ERROR_FAILURE);
+
+  LayoutDeviceIntPoint eventLoc =
+    aEvent->mRefPoint + aEvent->mWidget->WidgetToScreenOffset();
+  nsIntRect docFrameRect = docFrame->GetScreenRect(); // Returns CSS pixels
+  CSSIntPoint eventLocCSS(
+    mPresContext->DevPixelsToIntCSSPixels(eventLoc.x) - docFrameRect.x,
+    mPresContext->DevPixelsToIntCSSPixels(eventLoc.y) - docFrameRect.y);
+
+  Element* contentUnderMouse =
+    doc->ElementFromPointHelper(eventLocCSS.x, eventLocCSS.y, false, false);
+  if (contentUnderMouse) {
+    nsIWidget* targetWidget = nullptr;
+    nsIFrame* targetFrame = contentUnderMouse->GetPrimaryFrame();
+    nsIObjectFrame* pluginFrame = do_QueryFrame(targetFrame);
+    if (pluginFrame) {
+      targetWidget = pluginFrame->GetWidget();
+    } else if (targetFrame) {
+      targetWidget = targetFrame->GetNearestWidget();
+    }
+    if (aEvent->mWidget == targetWidget) {
+      aEvent->mReply.mWidgetIsHit = true;
+    }
+  }
+
+  aEvent->mSucceeded = true;
+  return NS_OK;
+}
+
+/* static */ nsresult
+ContentEventHandler::GetFlatTextLengthInRange(
+                       const NodePosition& aStartPosition,
+                       const NodePosition& aEndPosition,
+                       nsIContent* aRootContent,
+                       uint32_t* aLength,
+                       LineBreakType aLineBreakType,
+                       bool aIsRemovingNode /* = false */)
+{
+  if (NS_WARN_IF(!aRootContent) || NS_WARN_IF(!aStartPosition.IsValid()) ||
+      NS_WARN_IF(!aEndPosition.IsValid()) || NS_WARN_IF(!aLength)) {
+    return NS_ERROR_INVALID_ARG;
+  }
+
+  if (aStartPosition == aEndPosition) {
+    *aLength = 0;
+    return NS_OK;
+  }
+
+  // Don't create nsContentIterator instance until it's really necessary since
+  // destroying without initializing causes unexpected NS_ASSERTION() call.
+  nsCOMPtr<nsIContentIterator> iter;
+
+  // Working with ContentIterator, we may need to adjust the end position for
+  // including it forcibly.
+  NodePosition endPosition(aEndPosition);
+
+  // This may be called for retrieving the text of removed nodes.  Even in this
+  // case, the node thinks it's still in the tree because UnbindFromTree() will
+  // be called after here.  However, the node was already removed from the
+  // array of children of its parent.  So, be careful to handle this case.
+  if (aIsRemovingNode) {
+    DebugOnly<nsIContent*> parent = aStartPosition.mNode->GetParent();
+    MOZ_ASSERT(parent && parent->IndexOf(aStartPosition.mNode) == -1,
+      "At removing the node, the node shouldn't be in the array of children "
+      "of its parent");
+    MOZ_ASSERT(aStartPosition.mNode == endPosition.mNode,
+      "At removing the node, start and end node should be same");
+    MOZ_ASSERT(aStartPosition.mOffset == 0,
+      "When the node is being removed, the start offset should be 0");
+    MOZ_ASSERT(static_cast<uint32_t>(endPosition.mOffset) ==
+                 endPosition.mNode->GetChildCount(),
+      "When the node is being removed, the end offset should be child count");
+    iter = NS_NewPreContentIterator();
+    nsresult rv = iter->Init(aStartPosition.mNode);
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return rv;
+    }
+  } else {
+    RefPtr<nsRange> prev = new nsRange(aRootContent);
+    nsresult rv = aStartPosition.SetToRangeStart(prev);
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return rv;
+    }
+
+    // When the end position is immediately after non-root element's open tag,
+    // we need to include a line break caused by the open tag.
+    if (endPosition.mNode != aRootContent &&
+        endPosition.IsImmediatelyAfterOpenTag()) {
+      if (endPosition.mNode->HasChildren()) {
+        // When the end node has some children, move the end position to before
+        // the open tag of its first child.
+        nsINode* firstChild = endPosition.mNode->GetFirstChild();
+        if (NS_WARN_IF(!firstChild)) {
+          return NS_ERROR_FAILURE;
+        }
+        endPosition = NodePositionBefore(firstChild, 0);
+      } else {
+        // When the end node is empty, move the end position after the node.
+        nsIContent* parentContent = endPosition.mNode->GetParent();
+        if (NS_WARN_IF(!parentContent)) {
+          return NS_ERROR_FAILURE;
+        }
+        int32_t indexInParent = parentContent->IndexOf(endPosition.mNode);
+        if (NS_WARN_IF(indexInParent < 0)) {
+          return NS_ERROR_FAILURE;
+        }
+        endPosition = NodePositionBefore(parentContent, indexInParent + 1);
+      }
+    }
+
+    if (endPosition.OffsetIsValid()) {
+      // Offset is within node's length; set end of range to that offset
+      rv = endPosition.SetToRangeEnd(prev);
+      if (NS_WARN_IF(NS_FAILED(rv))) {
+        return rv;
+      }
+      iter = NS_NewPreContentIterator();
+      rv = iter->Init(prev);
+      if (NS_WARN_IF(NS_FAILED(rv))) {
+        return rv;
+      }
+    } else if (endPosition.mNode != aRootContent) {
+      // Offset is past node's length; set end of range to end of node
+      rv = endPosition.SetToRangeEndAfter(prev);
+      if (NS_WARN_IF(NS_FAILED(rv))) {
+        return rv;
+      }
+      iter = NS_NewPreContentIterator();
+      rv = iter->Init(prev);
+      if (NS_WARN_IF(NS_FAILED(rv))) {
+        return rv;
+      }
+    } else {
+      // Offset is past the root node; set end of range to end of root node
+      iter = NS_NewPreContentIterator();
+      rv = iter->Init(aRootContent);
+      if (NS_WARN_IF(NS_FAILED(rv))) {
+        return rv;
+      }
+    }
+  }
+
+  *aLength = 0;
+  for (; !iter->IsDone(); iter->Next()) {
+    nsINode* node = iter->GetCurrentNode();
+    if (NS_WARN_IF(!node)) {
+      break;
+    }
+    if (!node->IsContent()) {
+      continue;
+    }
+    nsIContent* content = node->AsContent();
+
+    if (node->IsNodeOfType(nsINode::eTEXT)) {
+      // Note: our range always starts from offset 0
+      if (node == endPosition.mNode) {
+        *aLength += GetTextLength(content, aLineBreakType,
+                                  endPosition.mOffset);
+      } else {
+        *aLength += GetTextLength(content, aLineBreakType);
+      }
+    } else if (ShouldBreakLineBefore(content, aRootContent)) {
+      // If the start position is start of this node but doesn't include the
+      // open tag, don't append the line break length.
+      if (node == aStartPosition.mNode && !aStartPosition.IsBeforeOpenTag()) {
+        continue;
+      }
+      // If the end position is before the open tag, don't append the line
+      // break length.
+      if (node == endPosition.mNode && endPosition.IsBeforeOpenTag()) {
+        continue;
+      }
+      *aLength += GetBRLength(aLineBreakType);
+    }
+  }
+  return NS_OK;
+}
+
+nsresult
+ContentEventHandler::GetStartOffset(nsRange* aRange,
+                                    uint32_t* aOffset,
+                                    LineBreakType aLineBreakType)
+{
+  MOZ_ASSERT(aRange);
+  return GetFlatTextLengthInRange(
+           NodePosition(mRootContent, 0),
+           NodePosition(aRange->GetStartParent(), aRange->StartOffset()),
+           mRootContent, aOffset, aLineBreakType);
+}
+
+nsresult
+ContentEventHandler::AdjustCollapsedRangeMaybeIntoTextNode(nsRange* aRange)
+{
+  MOZ_ASSERT(aRange);
+  MOZ_ASSERT(aRange->Collapsed());
+
+  if (!aRange || !aRange->Collapsed()) {
+    return NS_ERROR_INVALID_ARG;
+  }
+
+  nsCOMPtr<nsINode> parentNode = aRange->GetStartParent();
+  int32_t offsetInParentNode = aRange->StartOffset();
+  if (NS_WARN_IF(!parentNode) || NS_WARN_IF(offsetInParentNode < 0)) {
+    return NS_ERROR_INVALID_ARG;
+  }
+
+  // If the node is text node, we don't need to modify aRange.
+  if (parentNode->IsNodeOfType(nsINode::eTEXT)) {
+    return NS_OK;
+  }
+
+  // If the parent is not a text node but it has a text node at the offset,
+  // we should adjust the range into the text node.
+  // NOTE: This is emulating similar situation of EditorBase.
+  nsINode* childNode = nullptr;
+  int32_t offsetInChildNode = -1;
+  if (!offsetInParentNode && parentNode->HasChildren()) {
+    // If the range is the start of the parent, adjusted the range to the
+    // start of the first child.
+    childNode = parentNode->GetFirstChild();
+    offsetInChildNode = 0;
+  } else if (static_cast<uint32_t>(offsetInParentNode) <
+               parentNode->GetChildCount()) {
+    // If the range is next to a child node, adjust the range to the end of
+    // the previous child.
+    childNode = parentNode->GetChildAt(offsetInParentNode - 1);
+    offsetInChildNode = childNode->Length();
+  }
+
+  // But if the found node isn't a text node, we cannot modify the range.
+  if (!childNode || !childNode->IsNodeOfType(nsINode::eTEXT) ||
+      NS_WARN_IF(offsetInChildNode < 0)) {
+    return NS_OK;
+  }
+
+  nsresult rv = aRange->Set(childNode, offsetInChildNode,
+                            childNode, offsetInChildNode);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+  return NS_OK;
+}
+
+nsresult
+ContentEventHandler::GetStartFrameAndOffset(const nsRange* aRange,
+                                            nsIFrame*& aFrame,
+                                            int32_t& aOffsetInFrame)
+{
+  MOZ_ASSERT(aRange);
+
+  aFrame = nullptr;
+  aOffsetInFrame = -1;
+
+  nsINode* node = aRange->GetStartParent();
+  if (NS_WARN_IF(!node) ||
+      NS_WARN_IF(!node->IsNodeOfType(nsINode::eCONTENT))) {
+    return NS_ERROR_FAILURE;
+  }
+  nsIContent* content = static_cast<nsIContent*>(node);
+  RefPtr<nsFrameSelection> fs = mPresShell->FrameSelection();
+  aFrame = fs->GetFrameForNodeOffset(content, aRange->StartOffset(),
+                                     fs->GetHint(), &aOffsetInFrame);
+  if (NS_WARN_IF(!aFrame)) {
+    return NS_ERROR_FAILURE;
+  }
+  return NS_OK;
+}
+
+nsresult
+ContentEventHandler::ConvertToRootRelativeOffset(nsIFrame* aFrame,
+                                                 nsRect& aRect)
+{
+  NS_ASSERTION(aFrame, "aFrame must not be null");
+
+  nsPresContext* thisPC = aFrame->PresContext();
+  nsPresContext* rootPC = thisPC->GetRootPresContext();
+  if (NS_WARN_IF(!rootPC)) {
+    return NS_ERROR_FAILURE;
+  }
+  nsIFrame* rootFrame = rootPC->PresShell()->GetRootFrame();
+  if (NS_WARN_IF(!rootFrame)) {
+    return NS_ERROR_FAILURE;
+  }
+
+  aRect = nsLayoutUtils::TransformFrameRectToAncestor(aFrame, aRect, rootFrame);
+
+  // TransformFrameRectToAncestor returned the rect in the ancestor's appUnits,
+  // but we want it in aFrame's units (in case of different full-zoom factors),
+  // so convert back.
+  aRect = aRect.ScaleToOtherAppUnitsRoundOut(rootPC->AppUnitsPerDevPixel(),
+                                             thisPC->AppUnitsPerDevPixel());
+
+  return NS_OK;
+}
+
+static void AdjustRangeForSelection(nsIContent* aRoot,
+                                    nsINode** aNode,
+                                    int32_t* aNodeOffset)
+{
+  nsINode* node = *aNode;
+  int32_t nodeOffset = *aNodeOffset;
+  if (aRoot == node || NS_WARN_IF(!node->GetParent()) ||
+      !node->IsNodeOfType(nsINode::eTEXT)) {
+    return;
+  }
+
+  // When the offset is at the end of the text node, set it to after the
+  // text node, to make sure the caret is drawn on a new line when the last
+  // character of the text node is '\n' in <textarea>.
+  int32_t textLength =
+    static_cast<int32_t>(static_cast<nsIContent*>(node)->TextLength());
+  MOZ_ASSERT(nodeOffset <= textLength, "Offset is past length of text node");
+  if (nodeOffset != textLength) {
+    return;
+  }
+
+  nsIContent* aRootParent = aRoot->GetParent();
+  if (NS_WARN_IF(!aRootParent)) {
+    return;
+  }
+  // If the root node is not an anonymous div of <textarea>, we don't need to
+  // do this hack.  If you did this, ContentEventHandler couldn't distinguish
+  // if the range includes open tag of the next node in some cases, e.g.,
+  // textNode]<p></p> vs. textNode<p>]</p>
+  if (!aRootParent->IsHTMLElement(nsGkAtoms::textarea)) {
+    return;
+  }
+
+  *aNode = node->GetParent();
+  MOZ_ASSERT((*aNode)->IndexOf(node) != -1);
+  *aNodeOffset = (*aNode)->IndexOf(node) + 1;
+}
+
+nsresult
+ContentEventHandler::OnSelectionEvent(WidgetSelectionEvent* aEvent)
+{
+  aEvent->mSucceeded = false;
+
+  // Get selection to manipulate
+  // XXX why do we need to get them from ISM? This method should work fine
+  //     without ISM.
+  nsCOMPtr<nsISelection> sel;
+  nsresult rv =
+    IMEStateManager::GetFocusSelectionAndRoot(getter_AddRefs(sel),
+                                              getter_AddRefs(mRootContent));
+  mSelection = sel ? sel->AsSelection() : nullptr;
+  if (rv != NS_ERROR_NOT_AVAILABLE) {
+    NS_ENSURE_SUCCESS(rv, rv);
+  } else {
+    rv = Init(aEvent);
+    NS_ENSURE_SUCCESS(rv, rv);
+  }
+
+  // Get range from offset and length
+  RefPtr<nsRange> range = new nsRange(mRootContent);
+  rv = SetRangeFromFlatTextOffset(range, aEvent->mOffset, aEvent->mLength,
+                                  GetLineBreakType(aEvent),
+                                  aEvent->mExpandToClusterBoundary);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  nsINode* startNode = range->GetStartParent();
+  nsINode* endNode = range->GetEndParent();
+  int32_t startNodeOffset = range->StartOffset();
+  int32_t endNodeOffset = range->EndOffset();
+  AdjustRangeForSelection(mRootContent, &startNode, &startNodeOffset);
+  AdjustRangeForSelection(mRootContent, &endNode, &endNodeOffset);
+  if (NS_WARN_IF(!startNode) || NS_WARN_IF(!endNode) ||
+      NS_WARN_IF(startNodeOffset < 0) || NS_WARN_IF(endNodeOffset < 0)) {
+    return NS_ERROR_UNEXPECTED;
+  }
+
+  mSelection->StartBatchChanges();
+
+  // Clear selection first before setting
+  rv = mSelection->RemoveAllRanges();
+  // Need to call EndBatchChanges at the end even if call failed
+  if (NS_SUCCEEDED(rv)) {
+    if (aEvent->mReversed) {
+      rv = mSelection->Collapse(endNode, endNodeOffset);
+    } else {
+      rv = mSelection->Collapse(startNode, startNodeOffset);
+    }
+    if (NS_SUCCEEDED(rv) &&
+        (startNode != endNode || startNodeOffset != endNodeOffset)) {
+      if (aEvent->mReversed) {
+        rv = mSelection->Extend(startNode, startNodeOffset);
+      } else {
+        rv = mSelection->Extend(endNode, endNodeOffset);
+      }
+    }
+  }
+
+  // Pass the eSetSelection events reason along with the BatchChange-end
+  // selection change notifications.
+  mSelection->EndBatchChangesInternal(aEvent->mReason);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  mSelection->ScrollIntoViewInternal(
+    nsISelectionController::SELECTION_FOCUS_REGION,
+    false, nsIPresShell::ScrollAxis(), nsIPresShell::ScrollAxis());
+  aEvent->mSucceeded = true;
+  return NS_OK;
+}
+
+nsRect
+ContentEventHandler::FrameRelativeRect::RectRelativeTo(
+                                          nsIFrame* aDestFrame) const
+{
+  if (!mBaseFrame || NS_WARN_IF(!aDestFrame)) {
+    return nsRect();
+  }
+
+  if (NS_WARN_IF(aDestFrame->PresContext() != mBaseFrame->PresContext())) {
+    return nsRect();
+  }
+
+  if (aDestFrame == mBaseFrame) {
+    return mRect;
+  }
+
+  nsIFrame* rootFrame = mBaseFrame->PresContext()->PresShell()->GetRootFrame();
+  nsRect baseFrameRectInRootFrame =
+    nsLayoutUtils::TransformFrameRectToAncestor(mBaseFrame, nsRect(),
+                                                rootFrame);
+  nsRect destFrameRectInRootFrame =
+    nsLayoutUtils::TransformFrameRectToAncestor(aDestFrame, nsRect(),
+                                                rootFrame);
+  nsPoint difference =
+    destFrameRectInRootFrame.TopLeft() - baseFrameRectInRootFrame.TopLeft();
+  return mRect - difference;
+}
+
+} // namespace mozilla
-- 
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