1 files changed, 35 insertions, 0 deletions
diff --git a/layout/forms/nsTextControlFrame.h b/layout/forms/nsTextControlFrame.h
index a76cba514..9d4d0b77c 100644
--- a/layout/forms/nsTextControlFrame.h
+++ b/layout/forms/nsTextControlFrame.h
@@ -62,6 +62,29 @@ public:
                       const ReflowInput& aReflowInput,
                       nsReflowStatus&          aStatus) override;
 
+  bool GetVerticalAlignBaseline(mozilla::WritingMode aWM,
+                                nscoord* aBaseline) const override
+  {
+    return GetNaturalBaselineBOffset(aWM, BaselineSharingGroup::eFirst, aBaseline);
+  }
+
+  bool GetNaturalBaselineBOffset(mozilla::WritingMode aWM,
+                                 BaselineSharingGroup aBaselineGroup,
+                                 nscoord* aBaseline) const override
+  {
+    if (!IsSingleLineTextControl()) {
+      return false;
+    }
+    NS_ASSERTION(mFirstBaseline != NS_INTRINSIC_WIDTH_UNKNOWN,
+                 "please call Reflow before asking for the baseline");
+    if (aBaselineGroup == BaselineSharingGroup::eFirst) {
+      *aBaseline = mFirstBaseline;
+    } else {
+      *aBaseline = BSize(aWM) - mFirstBaseline;
+    }
+    return true;
+  }
+
   virtual nsSize GetXULMinSize(nsBoxLayoutState& aBoxLayoutState) override;
   virtual bool IsXULCollapsed() override;
 
@@ -87,6 +110,14 @@ public:
       ~(nsIFrame::eReplaced | nsIFrame::eReplacedContainsBlock));
   }
 
+#ifdef DEBUG
+  void MarkIntrinsicISizesDirty() override
+  {
+    // Need another Reflow to have a correct baseline value again.
+    mFirstBaseline = NS_INTRINSIC_WIDTH_UNKNOWN;
+  }
+#endif
+
   // nsIAnonymousContentCreator
   virtual nsresult CreateAnonymousContent(nsTArray<ContentInfo>& aElements) override;
   virtual void AppendAnonymousContentTo(nsTArray<nsIContent*>& aElements,
@@ -300,6 +331,10 @@ private:
   }
 
 private:
+  // Our first baseline, or NS_INTRINSIC_WIDTH_UNKNOWN if we have a pending
+  // Reflow.
+  nscoord mFirstBaseline;
+
   // these packed bools could instead use the high order bits on mState, saving 4 bytes 
   bool mEditorHasBeenInitialized;
   bool mIsProcessing;