Merge branch 'goanna-gfx'

9 files changed, 663 insertions, 2 deletions

diff --git a/image/DecoderFactory.cpp b/image/DecoderFactory.cpp
index 1c51d2fbc..2085fb7c4 100644
--- a/image/DecoderFactory.cpp
+++ b/image/DecoderFactory.cpp
@@ -5,6 +5,7 @@
 
 #include "DecoderFactory.h"
 
+#include "gfxPrefs.h"
 #include "nsMimeTypes.h"
 #include "mozilla/RefPtr.h"
 
@@ -17,6 +18,7 @@
 #include "nsBMPDecoder.h"
 #include "nsICODecoder.h"
 #include "nsIconDecoder.h"
+#include "nsWebPDecoder.h"
 
 namespace mozilla {
 
@@ -65,8 +67,12 @@ DecoderFactory::GetDecoderType(const char* aMimeType)
   // Icon
   } else if (!strcmp(aMimeType, IMAGE_ICON_MS)) {
     type = DecoderType::ICON;
-  }
 
+  // WebP
+  } else if (!strcmp(aMimeType, IMAGE_WEBP) &&
+             gfxPrefs::ImageWebPEnabled()) {
+    type = DecoderType::WEBP;
+  }
   return type;
 }
 
@@ -100,6 +106,9 @@ DecoderFactory::GetDecoder(DecoderType aType,
     case DecoderType::ICON:
       decoder = new nsIconDecoder(aImage);
       break;
+    case DecoderType::WEBP:
+      decoder = new nsWebPDecoder(aImage);
+      break;
     default:
       MOZ_ASSERT_UNREACHABLE("Unknown decoder type");
   }
@@ -171,7 +180,8 @@ DecoderFactory::CreateAnimationDecoder(DecoderType aType,
     return nullptr;
   }
 
-  MOZ_ASSERT(aType == DecoderType::GIF || aType == DecoderType::PNG,
+  MOZ_ASSERT(aType == DecoderType::GIF || aType == DecoderType::PNG ||
+             aType == DecoderType::WEBP,
              "Calling CreateAnimationDecoder for non-animating DecoderType");
 
   // Create an anonymous decoder. Interaction with the SurfaceCache and the
diff --git a/image/DecoderFactory.h b/image/DecoderFactory.h
index 107ebede6..f8cf64cc6 100644
--- a/image/DecoderFactory.h
+++ b/image/DecoderFactory.h
@@ -36,6 +36,7 @@ enum class DecoderType
   BMP,
   ICO,
   ICON,
+  WEBP,
   UNKNOWN
 };
 
diff --git a/image/build/nsImageModule.cpp b/image/build/nsImageModule.cpp
index 48d246cd3..9d52c07b6 100644
--- a/image/build/nsImageModule.cpp
+++ b/image/build/nsImageModule.cpp
@@ -82,6 +82,7 @@ static const mozilla::Module::CategoryEntry kImageCategories[] = {
   { "Gecko-Content-Viewers", IMAGE_PNG, "@mozilla.org/content/document-loader-factory;1" },
   { "Gecko-Content-Viewers", IMAGE_APNG, "@mozilla.org/content/document-loader-factory;1" },
   { "Gecko-Content-Viewers", IMAGE_X_PNG, "@mozilla.org/content/document-loader-factory;1" },
+  { "Gecko-Content-Viewers", IMAGE_WEBP, "@mozilla.org/content/document-loader-factory;1" },
   { "content-sniffing-services", "@mozilla.org/image/loader;1", "@mozilla.org/image/loader;1" },
   { nullptr }
 };
diff --git a/image/decoders/moz.build b/image/decoders/moz.build
index 775c3eaa5..30c026f99 100644
--- a/image/decoders/moz.build
+++ b/image/decoders/moz.build
@@ -28,6 +28,7 @@ UNIFIED_SOURCES += [
     'nsIconDecoder.cpp',
     'nsJPEGDecoder.cpp',
     'nsPNGDecoder.cpp',
+    'nsWebPDecoder.cpp',
 ]
 
 include('/ipc/chromium/chromium-config.mozbuild')
diff --git a/image/decoders/nsWebPDecoder.cpp b/image/decoders/nsWebPDecoder.cpp
new file mode 100644
index 000000000..5da696347
--- /dev/null
+++ b/image/decoders/nsWebPDecoder.cpp
@@ -0,0 +1,467 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ *
+ * 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 "ImageLogging.h" // Must appear first
+#include "nsWebPDecoder.h"
+
+#include "RasterImage.h"
+#include "SurfacePipeFactory.h"
+
+using namespace mozilla::gfx;
+
+namespace mozilla {
+namespace image {
+
+static LazyLogModule sWebPLog("WebPDecoder");
+
+nsWebPDecoder::nsWebPDecoder(RasterImage* aImage)
+  : Decoder(aImage)
+  , mLexer(Transition::ToUnbuffered(State::FINISHED_WEBP_DATA,
+                                    State::WEBP_DATA,
+                                    SIZE_MAX),
+           Transition::TerminateSuccess())
+  , mDecoder(nullptr)
+  , mBlend(BlendMethod::OVER)
+  , mDisposal(DisposalMethod::KEEP)
+  , mTimeout(FrameTimeout::Forever())
+  , mFormat(SurfaceFormat::B8G8R8X8)
+  , mLastRow(0)
+  , mCurrentFrame(0)
+{
+  MOZ_LOG(sWebPLog, LogLevel::Debug,
+      ("[this=%p] nsWebPDecoder::nsWebPDecoder", this));
+}
+
+nsWebPDecoder::~nsWebPDecoder()
+{
+  MOZ_LOG(sWebPLog, LogLevel::Debug,
+      ("[this=%p] nsWebPDecoder::~nsWebPDecoder", this));
+  WebPIDelete(mDecoder);
+}
+
+LexerResult
+nsWebPDecoder::DoDecode(SourceBufferIterator& aIterator, IResumable* aOnResume)
+{
+  MOZ_ASSERT(!HasError(), "Shouldn't call DoDecode after error!");
+
+  return mLexer.Lex(aIterator, aOnResume,
+                    [=](State aState, const char* aData, size_t aLength) {
+    switch (aState) {
+      case State::WEBP_DATA:
+        if (!HasSize()) {
+          return ReadHeader(aData, aLength);
+        }
+        return ReadPayload(aData, aLength);
+      case State::FINISHED_WEBP_DATA:
+        return FinishedData();
+    }
+    MOZ_CRASH("Unknown State");
+  });
+}
+
+nsresult
+nsWebPDecoder::CreateFrame(const nsIntRect& aFrameRect)
+{
+  MOZ_ASSERT(HasSize());
+  MOZ_ASSERT(!mDecoder);
+
+  MOZ_LOG(sWebPLog, LogLevel::Debug,
+      ("[this=%p] nsWebPDecoder::CreateFrame -- frame %u, %d x %d\n",
+       this, mCurrentFrame, aFrameRect.width, aFrameRect.height));
+
+  // If this is our first frame in an animation and it doesn't cover the
+  // full frame, then we are transparent even if there is no alpha
+  if (mCurrentFrame == 0 && !aFrameRect.IsEqualEdges(FullFrame())) {
+    MOZ_ASSERT(HasAnimation());
+    PostHasTransparency();
+  }
+
+  WebPInitDecBuffer(&mBuffer);
+  mBuffer.colorspace = MODE_RGBA;
+
+  mDecoder = WebPINewDecoder(&mBuffer);
+  if (!mDecoder) {
+    MOZ_LOG(sWebPLog, LogLevel::Error,
+        ("[this=%p] nsWebPDecoder::CreateFrame -- create decoder error\n",
+         this));
+    return NS_ERROR_FAILURE;
+  }
+
+  Maybe<SurfacePipe> pipe = SurfacePipeFactory::CreateSurfacePipe(this,
+      mCurrentFrame, Size(), OutputSize(), aFrameRect,
+      mFormat, SurfacePipeFlags());
+  if (!pipe) {
+    MOZ_LOG(sWebPLog, LogLevel::Error,
+        ("[this=%p] nsWebPDecoder::CreateFrame -- no pipe\n", this));
+    return NS_ERROR_FAILURE;
+  }
+
+  mPipe = Move(*pipe);
+  return NS_OK;
+}
+
+void
+nsWebPDecoder::EndFrame()
+{
+  MOZ_ASSERT(HasSize());
+  MOZ_ASSERT(mDecoder);
+
+  auto opacity = mFormat == SurfaceFormat::B8G8R8A8
+                 ? Opacity::SOME_TRANSPARENCY : Opacity::FULLY_OPAQUE;
+
+  MOZ_LOG(sWebPLog, LogLevel::Debug,
+      ("[this=%p] nsWebPDecoder::EndFrame -- frame %u, opacity %d, "
+       "disposal %d, timeout %d, blend %d\n",
+       this, mCurrentFrame, (int)opacity, (int)mDisposal,
+       mTimeout.AsEncodedValueDeprecated(), (int)mBlend));
+
+  PostFrameStop(opacity, mDisposal, mTimeout, mBlend);
+  WebPIDelete(mDecoder);
+  mDecoder = nullptr;
+  mLastRow = 0;
+  ++mCurrentFrame;
+}
+
+nsresult
+nsWebPDecoder::GetDataBuffer(const uint8_t*& aData, size_t& aLength)
+{
+  if (!mData.empty() && mData.begin() != aData) {
+    if (!mData.append(aData, aLength)) {
+      MOZ_LOG(sWebPLog, LogLevel::Error,
+          ("[this=%p] nsWebPDecoder::GetDataBuffer -- oom, append %zu on %zu\n",
+           this, aLength, mData.length()));
+      return NS_ERROR_OUT_OF_MEMORY;
+    }
+    aData = mData.begin();
+    aLength = mData.length();
+  }
+  return NS_OK;
+}
+
+nsresult
+nsWebPDecoder::SaveDataBuffer(const uint8_t* aData, size_t aLength)
+{
+  if (mData.empty() && !mData.append(aData, aLength)) {
+    MOZ_LOG(sWebPLog, LogLevel::Error,
+        ("[this=%p] nsWebPDecoder::SaveDataBuffer -- oom, append %zu on %zu\n",
+         this, aLength, mData.length()));
+    return NS_ERROR_OUT_OF_MEMORY;
+  }
+  return NS_OK;
+}
+
+LexerTransition<nsWebPDecoder::State>
+nsWebPDecoder::ReadHeader(const char* aData, size_t aLength)
+{
+  MOZ_LOG(sWebPLog, LogLevel::Debug,
+      ("[this=%p] nsWebPDecoder::ReadHeader -- %zu bytes\n", this, aLength));
+
+  // XXX(aosmond): In an ideal world, we could request the lexer to do this
+  // buffering for us (and in turn the underlying SourceBuffer). That way we
+  // could avoid extra copies during the decode and just do
+  // SourceBuffer::Compact on each iteration. For a typical WebP image we
+  // can hope that we will get the full header in the first packet, but
+  // for animated images we will end up buffering the whole stream if it
+  // not already fully received and contiguous.
+  auto data = (const uint8_t*)aData;
+  size_t length = aLength;
+  if (NS_FAILED(GetDataBuffer(data, length))) {
+    return Transition::TerminateFailure();
+  }
+
+  WebPBitstreamFeatures features;
+  VP8StatusCode status = WebPGetFeatures(data, length, &features);
+  switch (status) {
+    case VP8_STATUS_OK:
+      break;
+    case VP8_STATUS_NOT_ENOUGH_DATA:
+      if (NS_FAILED(SaveDataBuffer(data, length))) {
+        return Transition::TerminateFailure();
+      }
+      return Transition::ContinueUnbuffered(State::WEBP_DATA);
+    default:
+      MOZ_LOG(sWebPLog, LogLevel::Error,
+          ("[this=%p] nsWebPDecoder::ReadHeader -- parse error %d\n",
+           this, status));
+      return Transition::TerminateFailure();
+  }
+
+  if (features.has_animation) {
+    // A metadata decode expects to get the correct first frame timeout which
+    // sadly is not provided by the normal WebP header parsing.
+    WebPDemuxState state;
+    WebPData fragment;
+    fragment.bytes = data;
+    fragment.size = length;
+    WebPDemuxer* demuxer = WebPDemuxPartial(&fragment, &state);
+    if (!demuxer || state == WEBP_DEMUX_PARSE_ERROR) {
+      MOZ_LOG(sWebPLog, LogLevel::Error,
+          ("[this=%p] nsWebPDecoder::ReadHeader -- demux parse error\n", this));
+      WebPDemuxDelete(demuxer);
+      return Transition::TerminateFailure();
+    }
+
+    WebPIterator iter;
+    if (!WebPDemuxGetFrame(demuxer, 1, &iter)) {
+      WebPDemuxDelete(demuxer);
+      if (state == WEBP_DEMUX_DONE) {
+        MOZ_LOG(sWebPLog, LogLevel::Error,
+            ("[this=%p] nsWebPDecoder::ReadHeader -- demux parse error\n",
+             this));
+        return Transition::TerminateFailure();
+      }
+      if (NS_FAILED(SaveDataBuffer(data, length))) {
+        return Transition::TerminateFailure();
+      }
+      return Transition::ContinueUnbuffered(State::WEBP_DATA);
+    }
+
+    PostIsAnimated(FrameTimeout::FromRawMilliseconds(iter.duration));
+    WebPDemuxReleaseIterator(&iter);
+    WebPDemuxDelete(demuxer);
+  }
+
+  MOZ_LOG(sWebPLog, LogLevel::Debug,
+      ("[this=%p] nsWebPDecoder::ReadHeader -- %d x %d, alpha %d, "
+       "animation %d, format %d, metadata decode %d, first frame decode %d\n",
+       this, features.width, features.height, features.has_alpha,
+       features.has_animation, features.format, IsMetadataDecode(),
+       IsFirstFrameDecode()));
+
+  PostSize(features.width, features.height);
+  if (features.has_alpha) {
+    mFormat = SurfaceFormat::B8G8R8A8;
+    PostHasTransparency();
+  }
+
+  if (IsMetadataDecode()) {
+    return Transition::TerminateSuccess();
+  }
+
+  auto transition = ReadPayload((const char*)data, length);
+  if (!features.has_animation) {
+    mData.clearAndFree();
+  }
+  return transition;
+}
+
+LexerTransition<nsWebPDecoder::State>
+nsWebPDecoder::ReadPayload(const char* aData, size_t aLength)
+{
+  auto data = (const uint8_t*)aData;
+  if (!HasAnimation()) {
+    auto rv = ReadSingle(data, aLength, true, FullFrame());
+    if (rv.NextStateIsTerminal() &&
+        rv.NextStateAsTerminal() == TerminalState::SUCCESS) {
+      PostDecodeDone();
+    }
+    return rv;
+  }
+  return ReadMultiple(data, aLength);
+}
+
+LexerTransition<nsWebPDecoder::State>
+nsWebPDecoder::ReadSingle(const uint8_t* aData, size_t aLength, bool aAppend, const IntRect& aFrameRect)
+{
+  MOZ_ASSERT(!IsMetadataDecode());
+  MOZ_ASSERT(aData);
+  MOZ_ASSERT(aLength > 0);
+
+  MOZ_LOG(sWebPLog, LogLevel::Debug,
+      ("[this=%p] nsWebPDecoder::ReadSingle -- %zu bytes\n", this, aLength));
+
+  if (!mDecoder && NS_FAILED(CreateFrame(aFrameRect))) {
+    return Transition::TerminateFailure();
+  }
+
+  // XXX(aosmond): The demux API can be used for single images according to the
+  // documentation. If WebPIAppend is not any more efficient in its buffering
+  // than what we do for animated images, we should just combine the use cases.
+  bool complete;
+  VP8StatusCode status;
+  if (aAppend) {
+    status = WebPIAppend(mDecoder, aData, aLength);
+  } else {
+    status = WebPIUpdate(mDecoder, aData, aLength);
+  }
+  switch (status) {
+    case VP8_STATUS_OK:
+      complete = true;
+      break;
+    case VP8_STATUS_SUSPENDED:
+      complete = false;
+      break;
+    default:
+      MOZ_LOG(sWebPLog, LogLevel::Error,
+          ("[this=%p] nsWebPDecoder::ReadSingle -- append error %d\n",
+           this, status));
+      return Transition::TerminateFailure();
+  }
+
+  int lastRow = -1;
+  int width = 0;
+  int height = 0;
+  int stride = 0;
+  const uint8_t* rowStart = WebPIDecGetRGB(mDecoder, &lastRow, &width, &height, &stride);
+  if (!rowStart || lastRow == -1) {
+    return Transition::ContinueUnbuffered(State::WEBP_DATA);
+  }
+
+  if (width <= 0 || height <= 0 || stride <= 0) {
+    MOZ_LOG(sWebPLog, LogLevel::Error,
+        ("[this=%p] nsWebPDecoder::ReadSingle -- bad (w,h,s) = (%d, %d, %d)\n",
+         this, width, height, stride));
+    return Transition::TerminateFailure();
+  }
+
+  for (int row = mLastRow; row < lastRow; row++) {
+    const uint8_t* src = rowStart + row * stride;
+    auto result = mPipe.WritePixelsToRow<uint32_t>([&]() -> NextPixel<uint32_t> {
+      MOZ_ASSERT(mFormat == SurfaceFormat::B8G8R8A8 || src[3] == 0xFF);
+      const uint32_t pixel = gfxPackedPixel(src[3], src[0], src[1], src[2]);
+      src += 4;
+      return AsVariant(pixel);
+    });
+    MOZ_ASSERT(result != WriteState::FAILURE);
+    MOZ_ASSERT_IF(result == WriteState::FINISHED, complete && row == lastRow - 1);
+
+    if (result == WriteState::FAILURE) {
+      MOZ_LOG(sWebPLog, LogLevel::Error,
+          ("[this=%p] nsWebPDecoder::ReadSingle -- write pixels error\n",
+           this));
+      return Transition::TerminateFailure();
+    }
+  }
+
+  if (mLastRow != lastRow) {
+    mLastRow = lastRow;
+
+    Maybe<SurfaceInvalidRect> invalidRect = mPipe.TakeInvalidRect();
+    if (invalidRect) {
+      PostInvalidation(invalidRect->mInputSpaceRect,
+          Some(invalidRect->mOutputSpaceRect));
+    }
+  }
+
+  if (!complete) {
+    return Transition::ContinueUnbuffered(State::WEBP_DATA);
+  }
+
+  EndFrame();
+  return Transition::TerminateSuccess();
+}
+
+LexerTransition<nsWebPDecoder::State>
+nsWebPDecoder::ReadMultiple(const uint8_t* aData, size_t aLength)
+{
+  MOZ_ASSERT(!IsMetadataDecode());
+  MOZ_ASSERT(aData);
+
+  MOZ_LOG(sWebPLog, LogLevel::Debug,
+      ("[this=%p] nsWebPDecoder::ReadMultiple -- %zu bytes\n", this, aLength));
+
+  auto data = aData;
+  size_t length = aLength;
+  if (NS_FAILED(GetDataBuffer(data, length))) {
+    return Transition::TerminateFailure();
+  }
+
+  WebPDemuxState state;
+  WebPData fragment;
+  fragment.bytes = data;
+  fragment.size = length;
+  WebPDemuxer* demuxer = WebPDemuxPartial(&fragment, &state);
+  if (!demuxer) {
+    MOZ_LOG(sWebPLog, LogLevel::Error,
+        ("[this=%p] nsWebPDecoder::ReadMultiple -- create demuxer error\n",
+         this));
+    return Transition::TerminateFailure();
+  }
+
+  if (state == WEBP_DEMUX_PARSE_ERROR) {
+    MOZ_LOG(sWebPLog, LogLevel::Error,
+        ("[this=%p] nsWebPDecoder::ReadMultiple -- demuxer parse error\n",
+         this));
+    WebPDemuxDelete(demuxer);
+    return Transition::TerminateFailure();
+  }
+
+  bool complete = false;
+  WebPIterator iter;
+  auto rv = Transition::ContinueUnbuffered(State::WEBP_DATA);
+  if (WebPDemuxGetFrame(demuxer, mCurrentFrame + 1, &iter)) {
+    switch (iter.blend_method) {
+      case WEBP_MUX_BLEND:
+        mBlend = BlendMethod::OVER;
+        break;
+      case WEBP_MUX_NO_BLEND:
+        mBlend = BlendMethod::SOURCE;
+        break;
+      default:
+        MOZ_ASSERT_UNREACHABLE("Unhandled blend method");
+        break;
+    }
+
+    switch (iter.dispose_method) {
+      case WEBP_MUX_DISPOSE_NONE:
+        mDisposal = DisposalMethod::KEEP;
+        break;
+      case WEBP_MUX_DISPOSE_BACKGROUND:
+        mDisposal = DisposalMethod::CLEAR;
+        break;
+      default:
+        MOZ_ASSERT_UNREACHABLE("Unhandled dispose method");
+        break;
+    }
+
+    mFormat = iter.has_alpha ? SurfaceFormat::B8G8R8A8 : SurfaceFormat::B8G8R8X8;
+    mTimeout = FrameTimeout::FromRawMilliseconds(iter.duration);
+    nsIntRect frameRect(iter.x_offset, iter.y_offset, iter.width, iter.height);
+
+    rv = ReadSingle(iter.fragment.bytes, iter.fragment.size, false, frameRect);
+    complete = state == WEBP_DEMUX_DONE && !WebPDemuxNextFrame(&iter);
+    WebPDemuxReleaseIterator(&iter);
+  }
+
+  if (rv.NextStateIsTerminal()) {
+    if (rv.NextStateAsTerminal() == TerminalState::SUCCESS) {
+      // If we extracted one frame, and it is not the last, we need to yield to
+      // the lexer to allow the upper layers to acknowledge the frame.
+      if (!complete && !IsFirstFrameDecode()) {
+        // The resume point is determined by whether or not we had to buffer.
+        // If we have yet to buffer, we want to resume at the same point,
+        // otherwise our internal buffer has everything we need and we want
+        // to resume having consumed all of the current fragment.
+        rv = Transition::ContinueUnbufferedAfterYield(State::WEBP_DATA,
+                 mData.empty() ? 0 : aLength);
+      } else {
+        uint32_t loopCount = WebPDemuxGetI(demuxer, WEBP_FF_LOOP_COUNT);
+
+        MOZ_LOG(sWebPLog, LogLevel::Debug,
+          ("[this=%p] nsWebPDecoder::ReadMultiple -- loop count %u\n",
+           this, loopCount));
+        PostDecodeDone(loopCount - 1);
+      }
+    }
+  } else if (NS_FAILED(SaveDataBuffer(data, length))) {
+    rv = Transition::TerminateFailure();
+  }
+
+  WebPDemuxDelete(demuxer);
+  return rv;
+}
+
+LexerTransition<nsWebPDecoder::State>
+nsWebPDecoder::FinishedData()
+{
+  // Since we set up an unbuffered read for SIZE_MAX bytes, if we actually read
+  // all that data something is really wrong.
+  MOZ_ASSERT_UNREACHABLE("Read the entire address space?");
+  return Transition::TerminateFailure();
+}
+
+} // namespace image
+} // namespace mozilla
diff --git a/image/decoders/nsWebPDecoder.h b/image/decoders/nsWebPDecoder.h
new file mode 100644
index 000000000..5b3951cfc
--- /dev/null
+++ b/image/decoders/nsWebPDecoder.h
@@ -0,0 +1,91 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ *
+ * 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/. */
+
+#ifndef mozilla_image_decoders_nsWebPDecoder_h
+#define mozilla_image_decoders_nsWebPDecoder_h
+
+#include "Decoder.h"
+#include "webp/demux.h"
+#include "StreamingLexer.h"
+#include "SurfacePipe.h"
+
+namespace mozilla {
+namespace image {
+class RasterImage;
+
+class nsWebPDecoder : public Decoder
+{
+public:
+  virtual ~nsWebPDecoder();
+
+protected:
+  LexerResult DoDecode(SourceBufferIterator& aIterator,
+                       IResumable* aOnResume) override;
+
+private:
+  friend class DecoderFactory;
+
+  // Decoders should only be instantiated via DecoderFactory.
+  explicit nsWebPDecoder(RasterImage* aImage);
+
+  enum class State
+  {
+    WEBP_DATA,
+    FINISHED_WEBP_DATA
+  };
+
+  LexerTransition<State> ReadHeader(const char* aData, size_t aLength);
+  LexerTransition<State> ReadPayload(const char* aData, size_t aLength);
+  LexerTransition<State> FinishedData();
+
+  nsresult CreateFrame(const nsIntRect& aFrameRect);
+  void EndFrame();
+
+  nsresult GetDataBuffer(const uint8_t*& aData, size_t& aLength);
+  nsresult SaveDataBuffer(const uint8_t* aData, size_t aLength);
+
+  LexerTransition<State> ReadSingle(const uint8_t* aData, size_t aLength,
+                                    bool aAppend, const IntRect& aFrameRect);
+
+  LexerTransition<State> ReadMultiple(const uint8_t* aData, size_t aLength);
+
+  StreamingLexer<State> mLexer;
+
+  /// The SurfacePipe used to write to the output surface.
+  SurfacePipe mPipe;
+
+  /// The buffer used to accumulate data until the complete WebP header is received.
+  Vector<uint8_t> mData;
+
+  /// The libwebp output buffer descriptor pointing to the decoded data.
+  WebPDecBuffer mBuffer;
+
+  /// The libwebp incremental decoder descriptor, wraps mBuffer.
+  WebPIDecoder* mDecoder;
+
+  /// Blend method for the current frame.
+  BlendMethod mBlend;
+
+  /// Disposal method for the current frame.
+  DisposalMethod mDisposal;
+
+  /// Frame timeout for the current frame;
+  FrameTimeout mTimeout;
+
+  /// Surface format for the current frame.
+  gfx::SurfaceFormat mFormat;
+
+  /// The last row of decoded pixels written to mPipe.
+  int mLastRow;
+
+  /// Number of decoded frames.
+  uint32_t mCurrentFrame;
+};
+
+} // namespace image
+} // namespace mozilla
+
+#endif // mozilla_image_decoders_nsWebPDecoder_h
diff --git a/image/imgLoader.cpp b/image/imgLoader.cpp
index 3545c5be2..5e5ee7829 100644
--- a/image/imgLoader.cpp
+++ b/image/imgLoader.cpp
@@ -2558,6 +2558,11 @@ imgLoader::GetMimeTypeFromContent(const char* aContents,
                               !memcmp(aContents, "\000\000\002\000", 4))) {
     aContentType.AssignLiteral(IMAGE_ICO);
 
+  // WebPs always begin with RIFF, a 32-bit length, and WEBP.
+  } else if (aLength >= 12 && !memcmp(aContents, "RIFF", 4) &&
+                              !memcmp(aContents + 8, "WEBP", 4)) {
+    aContentType.AssignLiteral(IMAGE_WEBP);
+
   } else {
     /* none of the above?  I give up */
     return NS_ERROR_NOT_AVAILABLE;
diff --git a/image/test/gtest/TestLoader.cpp b/image/test/gtest/TestLoader.cpp
new file mode 100644
index 000000000..5551f3f05
--- /dev/null
+++ b/image/test/gtest/TestLoader.cpp
@@ -0,0 +1,84 @@
+/* -*- 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 "gtest/gtest.h"
+
+#include "Common.h"
+#include "imgLoader.h"
+#include "nsMimeTypes.h"
+#include "nsString.h"
+
+using namespace mozilla;
+using namespace mozilla::image;
+
+static void
+CheckMimeType(const char* aContents, size_t aLength, const char* aExpected)
+{
+  nsAutoCString detected;
+  nsresult rv = imgLoader::GetMimeTypeFromContent(aContents, aLength, detected);
+  if (aExpected) {
+    ASSERT_TRUE(NS_SUCCEEDED(rv));
+    EXPECT_TRUE(detected.EqualsASCII(aExpected));
+  } else {
+    ASSERT_TRUE(NS_FAILED(rv));
+    EXPECT_TRUE(detected.IsEmpty());
+  }
+}
+
+class ImageLoader : public ::testing::Test
+{
+protected:
+  AutoInitializeImageLib mInit;
+};
+
+TEST_F(ImageLoader, DetectGIF)
+{
+  const char buffer[] = "GIF87a";
+  CheckMimeType(buffer, sizeof(buffer), IMAGE_GIF);
+}
+
+TEST_F(ImageLoader, DetectPNG)
+{
+  const char buffer[] = "\x89\x50\x4E\x47\x0D\x0A\x1A\x0A";
+  CheckMimeType(buffer, sizeof(buffer), IMAGE_PNG);
+}
+
+TEST_F(ImageLoader, DetectJPEG)
+{
+  const char buffer[] = "\xFF\xD8\xFF";
+  CheckMimeType(buffer, sizeof(buffer), IMAGE_JPEG);
+}
+
+TEST_F(ImageLoader, DetectART)
+{
+  const char buffer[] = "\x4A\x47\xFF\xFF\x00";
+  CheckMimeType(buffer, sizeof(buffer), IMAGE_ART);
+}
+
+TEST_F(ImageLoader, DetectBMP)
+{
+  const char buffer[] = "BM";
+  CheckMimeType(buffer, sizeof(buffer), IMAGE_BMP);
+}
+
+TEST_F(ImageLoader, DetectICO)
+{
+  const char buffer[] = "\x00\x00\x01\x00";
+  CheckMimeType(buffer, sizeof(buffer), IMAGE_ICO);
+}
+
+TEST_F(ImageLoader, DetectWebP)
+{
+  const char buffer[] = "RIFF\xFF\xFF\xFF\xFFWEBPVP8L";
+  CheckMimeType(buffer, sizeof(buffer), IMAGE_WEBP);
+}
+
+TEST_F(ImageLoader, DetectNone)
+{
+  const char buffer[] = "abcdefghijklmnop";
+  CheckMimeType(buffer, sizeof(buffer), nullptr);
+}
+
diff --git a/image/test/gtest/moz.build b/image/test/gtest/moz.build
index 5cf6d5116..3548eaecc 100644
--- a/image/test/gtest/moz.build
+++ b/image/test/gtest/moz.build
@@ -13,6 +13,7 @@ UNIFIED_SOURCES = [
     'TestDecoders.cpp',
     'TestDecodeToSurface.cpp',
     'TestDeinterlacingFilter.cpp',
+    'TestLoader.cpp',
     'TestMetadata.cpp',
     'TestRemoveFrameRectFilter.cpp',
     'TestSourceBuffer.cpp',