Move WEBPImageDecoder to SkCodec

third_party/WebKit/Source/platform/image-decoders/webp/WEBPImageDecoder.cpp

Index: third_party/WebKit/Source/platform/image-decoders/webp/WEBPImageDecoder.cpp
diff --git a/third_party/WebKit/Source/platform/image-decoders/webp/WEBPImageDecoder.cpp b/third_party/WebKit/Source/platform/image-decoders/webp/WEBPImageDecoder.cpp
index 1d4fad0d7b04f22945c55797e81fc03dff5a05e2..5902e38b47db0fa882ea0f317fcaafa7dbb66e74 100644
--- a/third_party/WebKit/Source/platform/image-decoders/webp/WEBPImageDecoder.cpp
+++ b/third_party/WebKit/Source/platform/image-decoders/webp/WEBPImageDecoder.cpp
@@ -28,94 +28,11 @@
 
 #include "platform/image-decoders/webp/WEBPImageDecoder.h"
 
-#include "build/build_config.h"
-#include "third_party/skia/include/core/SkData.h"
-
-#if defined(ARCH_CPU_BIG_ENDIAN)
-#error Blink assumes a little-endian target.
-#endif
-
-#if SK_B32_SHIFT  // Output little-endian RGBA pixels (Android).
-inline WEBP_CSP_MODE outputMode(bool hasAlpha) {
-  return hasAlpha ? MODE_rgbA : MODE_RGBA;
-}
-#else  // Output little-endian BGRA pixels.
-inline WEBP_CSP_MODE outputMode(bool hasAlpha) {
-  return hasAlpha ? MODE_bgrA : MODE_BGRA;
-}
-#endif
-
-namespace {
-
-// Returns two point ranges (<left, width> pairs) at row |canvasY| which belong
-// to |src| but not |dst|. A range is empty if its width is 0.
-inline void findBlendRangeAtRow(const blink::IntRect& src,
-                                const blink::IntRect& dst,
-                                int canvasY,
-                                int& left1,
-                                int& width1,
-                                int& left2,
-                                int& width2) {
-  SECURITY_DCHECK(canvasY >= src.Y() && canvasY < src.MaxY());
-  left1 = -1;
-  width1 = 0;
-  left2 = -1;
-  width2 = 0;
-
-  if (canvasY < dst.Y() || canvasY >= dst.MaxY() || src.X() >= dst.MaxX() ||
-      src.MaxX() <= dst.X()) {
-    left1 = src.X();
-    width1 = src.Width();
-    return;
-  }
-
-  if (src.X() < dst.X()) {
-    left1 = src.X();
-    width1 = dst.X() - src.X();
-  }
-
-  if (src.MaxX() > dst.MaxX()) {
-    left2 = dst.MaxX();
-    width2 = src.MaxX() - dst.MaxX();
-  }
-}
-
-// alphaBlendPremultiplied and alphaBlendNonPremultiplied are separate methods,
-// even though they only differ by one line. This is done so that the compiler
-// can inline BlendSrcOverDstPremultiplied() and BlensSrcOverDstRaw() calls.
-// For GIF images, this optimization reduces decoding time by 15% for 3MB
-// images.
-void alphaBlendPremultiplied(blink::ImageFrame& src,
-                             blink::ImageFrame& dst,
-                             int canvasY,
-                             int left,
-                             int width) {
-  for (int x = 0; x < width; ++x) {
-    int canvasX = left + x;
-    blink::ImageFrame::PixelData* pixel = src.GetAddr(canvasX, canvasY);
-    if (SkGetPackedA32(*pixel) != 0xff) {
-      blink::ImageFrame::PixelData prevPixel = *dst.GetAddr(canvasX, canvasY);
-      blink::ImageFrame::BlendSrcOverDstPremultiplied(pixel, prevPixel);
-    }
-  }
-}
-
-void alphaBlendNonPremultiplied(blink::ImageFrame& src,
-                                blink::ImageFrame& dst,
-                                int canvasY,
-                                int left,
-                                int width) {
-  for (int x = 0; x < width; ++x) {
-    int canvasX = left + x;
-    blink::ImageFrame::PixelData* pixel = src.GetAddr(canvasX, canvasY);
-    if (SkGetPackedA32(*pixel) != 0xff) {
-      blink::ImageFrame::PixelData prevPixel = *dst.GetAddr(canvasX, canvasY);
-      blink::ImageFrame::BlendSrcOverDstRaw(pixel, prevPixel);
-    }
-  }
-}
-
-}  // namespace
+#include <limits>
+#include "platform/image-decoders/SegmentStream.h"
+#include "platform/wtf/NotFound.h"
+#include "platform/wtf/PtrUtil.h"
+#include "third_party/skia/include/core/SkImageInfo.h"
 
 namespace blink {
 
@@ -123,406 +40,281 @@ WEBPImageDecoder::WEBPImageDecoder(AlphaOption alpha_option,
                                    const ColorBehavior& color_behavior,
                                    size_t max_decoded_bytes)
     : ImageDecoder(alpha_option, color_behavior, max_decoded_bytes),
-      decoder_(0),
-      format_flags_(0),
-      frame_background_has_alpha_(false),
-      demux_(0),
-      demux_state_(WEBP_DEMUX_PARSING_HEADER),
-      have_already_parsed_this_data_(false),
-      repetition_count_(kAnimationLoopOnce),
-      decoded_height_(0) {
-  blend_function_ = (alpha_option == kAlphaPremultiplied)
-                        ? alphaBlendPremultiplied
-                        : alphaBlendNonPremultiplied;
-}
+      codec_(),
+      segment_stream_(nullptr) {}
 
-WEBPImageDecoder::~WEBPImageDecoder() {
-  Clear();
-}
+WEBPImageDecoder::~WEBPImageDecoder() = default;
 
-void WEBPImageDecoder::Clear() {
-  WebPDemuxDelete(demux_);
-  demux_ = 0;
-  consolidated_data_.reset();
-  ClearDecoder();
-}
+void WEBPImageDecoder::OnSetData(SegmentReader* data) {
+  if (!data) {
+    if (segment_stream_)
+      segment_stream_->SetReader(nullptr);
+    return;
+  }
 
-void WEBPImageDecoder::ClearDecoder() {
-  WebPIDelete(decoder_);
-  decoder_ = 0;
-  decoded_height_ = 0;
-  frame_background_has_alpha_ = false;
-}
+  std::unique_ptr<SegmentStream> segment_stream;
+  if (!segment_stream_) {
+    segment_stream = base::MakeUnique<SegmentStream>();
+    segment_stream_ = segment_stream.get();
+  }
 
-void WEBPImageDecoder::OnSetData(SegmentReader*) {
-  have_already_parsed_this_data_ = false;
+  segment_stream_->SetReader(std::move(data));
+
+  if (!codec_) {
+    SkCodec::Result codec_creation_result;
+    codec_ = SkCodec::MakeFromStream(std::move(segment_stream),
+                                     &codec_creation_result, nullptr);
+    switch (codec_creation_result) {
+      case SkCodec::kSuccess: {
+        // SkCodec::MakeFromStream will read enough of the image to get the
+        // image size.
+        SkImageInfo image_info = codec_->getInfo();
+        SetSize(image_info.width(), image_info.height());
+        return;
+      }
+      case SkCodec::kIncompleteInput:
+        // |segment_stream_|'s ownership is passed into MakeFromStream.
+        // It is deleted if MakeFromStream fails.
+        // If MakeFromStream fails, we set |segment_stream_| to null so
+        // we aren't pointing to reclaimed memory.
+        segment_stream_ = nullptr;
+        return;
+      default:
+        SetFailed();
+        return;
+    }
+  }
 }
 
 int WEBPImageDecoder::RepetitionCount() const {
-  return Failed() ? kAnimationLoopOnce : repetition_count_;
+  if (!codec_ || segment_stream_->IsCleared())
+    return repetition_count_;
+
+  DCHECK(!Failed());
+
+  // SkCodec will parse forward in the file if the repetition count has not
+  // been seen yet.
+  int repetition_count = codec_->getRepetitionCount();
+
+  switch (repetition_count) {
+    case 0: {
+      // SkCodec returns 0 for both still images and animated images which
+      // only play once.
+      if (IsAllDataReceived() && codec_->getFrameCount() == 1) {
+        repetition_count_ = kAnimationNone;
+        break;
+      }
+
+      repetition_count_ = kAnimationLoopOnce;
+      break;
+    }
+    case SkCodec::kRepetitionCountInfinite:
+      repetition_count_ = kAnimationLoopInfinite;
+      break;
+    default:
+      repetition_count_ = repetition_count;
+      break;
+  }
+
+  return repetition_count_;
 }
 
 bool WEBPImageDecoder::FrameIsReceivedAtIndex(size_t index) const {
-  if (!demux_ || demux_state_ <= WEBP_DEMUX_PARSING_HEADER)
+  SkCodec::FrameInfo frame_info;
+  if (!codec_ || !codec_->getFrameInfo(index, &frame_info))
     return false;
-  if (!(format_flags_ & ANIMATION_FLAG))
-    return ImageDecoder::FrameIsReceivedAtIndex(index);
-  bool frame_is_received_at_index = index < frame_buffer_cache_.size();
-  return frame_is_received_at_index;
+  return frame_info.fFullyReceived;
 }
 
 float WEBPImageDecoder::FrameDurationAtIndex(size_t index) const {
-  return index < frame_buffer_cache_.size()
-             ? frame_buffer_cache_[index].Duration()
-             : 0;
+  if (index < frame_buffer_cache_.size())
+    return frame_buffer_cache_[index].Duration();
+  return 0;
 }
 
-bool WEBPImageDecoder::UpdateDemuxer() {
-  if (Failed())
-    return false;
-
-  if (have_already_parsed_this_data_)
-    return true;
-
-  have_already_parsed_this_data_ = true;
-
-  const unsigned kWebpHeaderSize = 30;
-  if (data_->size() < kWebpHeaderSize)
-    return false;  // Await VP8X header so WebPDemuxPartial succeeds.
-
-  WebPDemuxDelete(demux_);
-  consolidated_data_ = data_->GetAsSkData();
-  WebPData input_data = {
-      reinterpret_cast<const uint8_t*>(consolidated_data_->data()),
-      consolidated_data_->size()};
-  demux_ = WebPDemuxPartial(&input_data, &demux_state_);
-  if (!demux_ || (IsAllDataReceived() && demux_state_ != WEBP_DEMUX_DONE)) {
-    if (!demux_)
-      consolidated_data_.reset();
-    return SetFailed();
-  }
-
-  DCHECK_GT(demux_state_, WEBP_DEMUX_PARSING_HEADER);
-  if (!WebPDemuxGetI(demux_, WEBP_FF_FRAME_COUNT))
-    return false;  // Wait until the encoded image frame data arrives.
-
-  if (!IsDecodedSizeAvailable()) {
-    int width = WebPDemuxGetI(demux_, WEBP_FF_CANVAS_WIDTH);
-    int height = WebPDemuxGetI(demux_, WEBP_FF_CANVAS_HEIGHT);
-    if (!SetSize(width, height))
-      return SetFailed();
-
-    format_flags_ = WebPDemuxGetI(demux_, WEBP_FF_FORMAT_FLAGS);
-    if (!(format_flags_ & ANIMATION_FLAG)) {
-      repetition_count_ = kAnimationNone;
-    } else {
-      // Since we have parsed at least one frame, even if partially,
-      // the global animation (ANIM) properties have been read since
-      // an ANIM chunk must precede the ANMF frame chunks.
-      repetition_count_ = WebPDemuxGetI(demux_, WEBP_FF_LOOP_COUNT);
-      // Repetition count is always <= 16 bits.
-      DCHECK_EQ(repetition_count_, repetition_count_ & 0xffff);
-      if (!repetition_count_)
-        repetition_count_ = kAnimationLoopInfinite;
-      // FIXME: Implement ICC profile support for animated images.
-      format_flags_ &= ~ICCP_FLAG;
-    }
+bool WEBPImageDecoder::SetFailed() {
+  segment_stream_ = nullptr;
+  codec_.reset();
+  return ImageDecoder::SetFailed();
+}
 
-    if ((format_flags_ & ICCP_FLAG) && !IgnoresColorSpace())
-      ReadColorProfile();
+size_t WEBPImageDecoder::ClearCacheExceptFrame(size_t index) {
+  // SkCodec attempts to report the earliest possible required frame, but it is
+  // possible that frame has been evicted, while a later frame (which could also
+  // be used as the required frame) is still cached. Try to preserve a frame
+  // that is still cached.
+  if (frame_buffer_cache_.size() <= 1)
+    return 0;
+
+  size_t index2 = kNotFound;
+  if (index < frame_buffer_cache_.size()) {
+    const ImageFrame& frame = frame_buffer_cache_[index];
+    if (frame.RequiredPreviousFrameIndex() != kNotFound &&
+        !FrameStatusSufficientForSuccessors(index))
+      index2 = GetViableReferenceFrameIndex(index);
   }
 
-  DCHECK(IsDecodedSizeAvailable());
+  return ClearCacheExceptTwoFrames(index, index2);
+}
 
-  size_t frame_count = WebPDemuxGetI(demux_, WEBP_FF_FRAME_COUNT);
-  UpdateAggressivePurging(frame_count);
+size_t WEBPImageDecoder::DecodeFrameCount() {
+  if (!codec_ || segment_stream_->IsCleared())
+    return frame_buffer_cache_.size();
 
-  return true;
+  return codec_->getFrameCount();
 }
 
-void WEBPImageDecoder::OnInitFrameBuffer(size_t frame_index) {
-  // ImageDecoder::InitFrameBuffer does a DCHECK if |frame_index| exists.
-  ImageFrame& buffer = frame_buffer_cache_[frame_index];
-
-  const size_t required_previous_frame_index =
-      buffer.RequiredPreviousFrameIndex();
-  if (required_previous_frame_index == kNotFound) {
-    frame_background_has_alpha_ =
-        !buffer.OriginalFrameRect().Contains(IntRect(IntPoint(), Size()));
+void WEBPImageDecoder::InitializeNewFrame(size_t index) {
+  DCHECK(codec_);
+
+  ImageFrame& frame = frame_buffer_cache_[index];
+  // SkCodec does not inform us if only a portion of the image was updated
+  // in the current frame. Because of this, rather than correctly filling in
+  // the frame rect, we set the frame rect to be the image's full size.
+  // The original frame rect is not used, anyway.
+  IntSize full_image_size = Size();
+  frame.SetOriginalFrameRect(IntRect(IntPoint(), full_image_size));
+
+  SkCodec::FrameInfo frame_info;
+  bool frame_info_received = codec_->getFrameInfo(index, &frame_info);
+  DCHECK(frame_info_received);
+  frame.SetDuration(frame_info.fDuration);
+  size_t required_previous_frame_index;
+  if (frame_info.fRequiredFrame == SkCodec::kNone) {
+    required_previous_frame_index = WTF::kNotFound;
   } else {
-    const ImageFrame& prev_buffer =
-        frame_buffer_cache_[required_previous_frame_index];
-    frame_background_has_alpha_ =
-        prev_buffer.HasAlpha() || (prev_buffer.GetDisposalMethod() ==
-                                   ImageFrame::kDisposeOverwriteBgcolor);
+    required_previous_frame_index =
+        static_cast<size_t>(frame_info.fRequiredFrame);
   }
+  frame.SetRequiredPreviousFrameIndex(required_previous_frame_index);
 
-  // The buffer is transparent outside the decoded area while the image is
-  // loading. The correct alpha value for the frame will be set when it is fully
-  // decoded.
-  buffer.SetHasAlpha(true);
-}
-
-bool WEBPImageDecoder::CanReusePreviousFrameBuffer(size_t frame_index) const {
-  DCHECK(frame_index < frame_buffer_cache_.size());
-  return frame_buffer_cache_[frame_index].GetAlphaBlendSource() !=
-         ImageFrame::kBlendAtopPreviousFrame;
-}
-
-void WEBPImageDecoder::ClearFrameBuffer(size_t frame_index) {
-  if (demux_ && demux_state_ >= WEBP_DEMUX_PARSED_HEADER &&
-      frame_buffer_cache_[frame_index].GetStatus() ==
-          ImageFrame::kFramePartial) {
-    // Clear the decoder state so that this partial frame can be decoded again
-    // when requested.
-    ClearDecoder();
+  ImageFrame::DisposalMethod disposal_method = ImageFrame::kDisposeNotSpecified;
+  switch (frame_info.fDisposalMethod) {
+    case SkCodecAnimation::DisposalMethod::kKeep:
+      disposal_method = ImageFrame::kDisposeKeep;
+      break;
+    case SkCodecAnimation::DisposalMethod::kRestoreBGColor:
+      disposal_method = ImageFrame::kDisposeOverwriteBgcolor;
+      break;
+    default:
+      break;
   }
-  ImageDecoder::ClearFrameBuffer(frame_index);
+  frame.SetDisposalMethod(disposal_method);
 }
 
-void WEBPImageDecoder::ReadColorProfile() {
-  WebPChunkIterator chunk_iterator;
-  if (!WebPDemuxGetChunk(demux_, "ICCP", 1, &chunk_iterator)) {
-    WebPDemuxReleaseChunkIterator(&chunk_iterator);
+void WEBPImageDecoder::Decode(size_t index) {
+  if (!codec_ || segment_stream_->IsCleared())
     return;
-  }
 
-  const char* profile_data =
-      reinterpret_cast<const char*>(chunk_iterator.chunk.bytes);
-  size_t profile_size = chunk_iterator.chunk.size;
+  DCHECK(!Failed());
 
-  SetEmbeddedColorProfile(profile_data, profile_size);
+  DCHECK_LT(index, frame_buffer_cache_.size());
 
-  WebPDemuxReleaseChunkIterator(&chunk_iterator);
-}
+  UpdateAggressivePurging(index);
+  SkImageInfo image_info = codec_->getInfo()
+                               .makeColorType(kN32_SkColorType)
+                               .makeColorSpace(ColorSpaceForSkImages());
 
-void WEBPImageDecoder::ApplyPostProcessing(size_t frame_index) {
-  ImageFrame& buffer = frame_buffer_cache_[frame_index];
-  int width;
-  int decoded_height;
-  if (!WebPIDecGetRGB(decoder_, &decoded_height, &width, 0, 0))
-    return;  // See also https://bugs.webkit.org/show_bug.cgi?id=74062
-  if (decoded_height <= 0)
-    return;
+  SkCodec::Options options;
+  options.fFrameIndex = index;
+  options.fPriorFrame = SkCodec::kNone;
+  options.fZeroInitialized = SkCodec::kNo_ZeroInitialized;
 
-  const IntRect& frame_rect = buffer.OriginalFrameRect();
-  SECURITY_DCHECK(width == frame_rect.Width());
-  SECURITY_DCHECK(decoded_height <= frame_rect.Height());
-  const int left = frame_rect.X();
-  const int top = frame_rect.Y();
-
-  // TODO (msarett):
-  // Here we apply the color space transformation to the dst space.
-  // It does not really make sense to transform to a gamma-encoded
-  // space and then immediately after, perform a linear premultiply
-  // and linear blending.  Can we find a way to perform the
-  // premultiplication and blending in a linear space?
-  SkColorSpaceXform* xform = ColorTransform();
-  if (xform) {
-    const SkColorSpaceXform::ColorFormat kSrcFormat =
-        SkColorSpaceXform::kBGRA_8888_ColorFormat;
-    const SkColorSpaceXform::ColorFormat kDstFormat =
-        SkColorSpaceXform::kRGBA_8888_ColorFormat;
-    for (int y = decoded_height_; y < decoded_height; ++y) {
-      const int canvas_y = top + y;
-      uint8_t* row = reinterpret_cast<uint8_t*>(buffer.GetAddr(left, canvas_y));
-      xform->apply(kDstFormat, row, kSrcFormat, row, width,
-                   kUnpremul_SkAlphaType);
-
-      uint8_t* pixel = row;
-      for (int x = 0; x < width; ++x, pixel += 4) {
-        const int canvas_x = left + x;
-        buffer.SetRGBA(canvas_x, canvas_y, pixel[0], pixel[1], pixel[2],
-                       pixel[3]);
+  ImageFrame& frame = frame_buffer_cache_[index];
+  if (frame.GetStatus() == ImageFrame::kFrameEmpty) {
+    size_t required_previous_frame_index = frame.RequiredPreviousFrameIndex();
+    if (required_previous_frame_index == kNotFound) {
+      frame.AllocatePixelData(Size().Width(), Size().Height(),
+                              ColorSpaceForSkImages());
+      frame.ZeroFillPixelData();
+    } else {
+      size_t previous_frame_index = GetViableReferenceFrameIndex(index);
+      if (previous_frame_index == kNotFound) {
+        previous_frame_index = required_previous_frame_index;
+        Decode(previous_frame_index);
       }
-    }
-  }
 
-  // During the decoding of the current frame, we may have set some pixels to be
-  // transparent (i.e. alpha < 255). If the alpha blend source was
-  // 'BlendAtopPreviousFrame', the values of these pixels should be determined
-  // by blending them against the pixels of the corresponding previous frame.
-  // Compute the correct opaque values now.
-  // FIXME: This could be avoided if libwebp decoder had an API that used the
-  // previous required frame to do the alpha-blending by itself.
-  if ((format_flags_ & ANIMATION_FLAG) && frame_index &&
-      buffer.GetAlphaBlendSource() == ImageFrame::kBlendAtopPreviousFrame &&
-      buffer.RequiredPreviousFrameIndex() != kNotFound) {
-    ImageFrame& prev_buffer = frame_buffer_cache_[frame_index - 1];
-    DCHECK_EQ(prev_buffer.GetStatus(), ImageFrame::kFrameComplete);
-    ImageFrame::DisposalMethod prev_disposal_method =
-        prev_buffer.GetDisposalMethod();
-    if (prev_disposal_method == ImageFrame::kDisposeKeep) {
-      // Blend transparent pixels with pixels in previous canvas.
-      for (int y = decoded_height_; y < decoded_height; ++y) {
-        blend_function_(buffer, prev_buffer, top + y, left, width);
-      }
-    } else if (prev_disposal_method == ImageFrame::kDisposeOverwriteBgcolor) {
-      const IntRect& prev_rect = prev_buffer.OriginalFrameRect();
-      // We need to blend a transparent pixel with the starting value (from just
-      // after the InitFrame() call). If the pixel belongs to prev_rect, the
-      // starting value was fully transparent, so this is a no-op. Otherwise, we
-      // need to blend against the pixel from the previous canvas.
-      for (int y = decoded_height_; y < decoded_height; ++y) {
-        int canvas_y = top + y;
-        int left1, width1, left2, width2;
-        findBlendRangeAtRow(frame_rect, prev_rect, canvas_y, left1, width1,
-                            left2, width2);
-        if (width1 > 0)
-          blend_function_(buffer, prev_buffer, canvas_y, left1, width1);
-        if (width2 > 0)
-          blend_function_(buffer, prev_buffer, canvas_y, left2, width2);
+      // We try to reuse |previous_frame| as starting state to avoid copying.
+      // If CanReusePreviousFrameBuffer returns false, we must copy the data
+      // since |previous_frame| is necessary to decode this or later frames.
+      // In that case copy the data instead.
+      ImageFrame& previous_frame = frame_buffer_cache_[previous_frame_index];
+      if (!frame.TakeBitmapDataIfWritable(&previous_frame) &&
+          !frame.CopyBitmapData(previous_frame)) {
+        SetFailed();
+        return;
       }
+      options.fPriorFrame = previous_frame_index;
     }
   }
 
-  decoded_height_ = decoded_height;
-  buffer.SetPixelsChanged(true);
-}
-
-size_t WEBPImageDecoder::DecodeFrameCount() {
-  // If UpdateDemuxer() fails, return the existing number of frames.  This way
-  // if we get halfway through the image before decoding fails, we won't
-  // suddenly start reporting that the image has zero frames.
-  return UpdateDemuxer() ? WebPDemuxGetI(demux_, WEBP_FF_FRAME_COUNT)
-                         : frame_buffer_cache_.size();
-}
-
-void WEBPImageDecoder::InitializeNewFrame(size_t index) {
-  if (!(format_flags_ & ANIMATION_FLAG)) {
-    DCHECK(!index);
-    return;
+  if (frame.GetStatus() == ImageFrame::kFrameAllocated) {
+    SkCodec::Result start_incremental_decode_result =
+        codec_->startIncrementalDecode(image_info, frame.Bitmap().getPixels(),
+                                       frame.Bitmap().rowBytes(), &options);
+    switch (start_incremental_decode_result) {
+      case SkCodec::kSuccess:
+        break;
+      case SkCodec::kIncompleteInput:
+        return;
+      default:
+        SetFailed();
+        return;
+    }
+    frame.SetStatus(ImageFrame::kFramePartial);
   }
-  WebPIterator animated_frame;
-  WebPDemuxGetFrame(demux_, index + 1, &animated_frame);
-  DCHECK_EQ(animated_frame.complete, 1);
-  ImageFrame* buffer = &frame_buffer_cache_[index];
-  IntRect frame_rect(animated_frame.x_offset, animated_frame.y_offset,
-                     animated_frame.width, animated_frame.height);
-  buffer->SetOriginalFrameRect(
-      Intersection(frame_rect, IntRect(IntPoint(), Size())));
-  buffer->SetDuration(animated_frame.duration);
-  buffer->SetDisposalMethod(animated_frame.dispose_method ==
-                                    WEBP_MUX_DISPOSE_BACKGROUND
-                                ? ImageFrame::kDisposeOverwriteBgcolor
-                                : ImageFrame::kDisposeKeep);
-  buffer->SetAlphaBlendSource(animated_frame.blend_method == WEBP_MUX_BLEND
-                                  ? ImageFrame::kBlendAtopPreviousFrame
-                                  : ImageFrame::kBlendAtopBgcolor);
-  buffer->SetRequiredPreviousFrameIndex(
-      FindRequiredPreviousFrame(index, !animated_frame.has_alpha));
-  WebPDemuxReleaseIterator(&animated_frame);
-}
 
-void WEBPImageDecoder::Decode(size_t index) {
-  if (Failed())
-    return;
-
-  Vector<size_t> frames_to_decode = FindFramesToDecode(index);
-
-  DCHECK(demux_);
-  for (auto i = frames_to_decode.rbegin(); i != frames_to_decode.rend(); ++i) {
-    if ((format_flags_ & ANIMATION_FLAG) && !InitFrameBuffer(*i)) {
-      SetFailed();
-      return;
+  SkCodec::Result incremental_decode_result = codec_->incrementalDecode();
+  switch (incremental_decode_result) {
+    case SkCodec::kSuccess: {
+      SkCodec::FrameInfo frame_info;
+      bool frame_info_received = codec_->getFrameInfo(index, &frame_info);
+      DCHECK(frame_info_received);
+      frame.SetHasAlpha(!SkAlphaTypeIsOpaque(frame_info.fAlphaType));
+      frame.SetPixelsChanged(true);
+      frame.SetStatus(ImageFrame::kFrameComplete);
+      PostDecodeProcessing(index);
+      break;
     }
-
-    WebPIterator webp_frame;
-    if (!WebPDemuxGetFrame(demux_, *i + 1, &webp_frame)) {
+    case SkCodec::kIncompleteInput:
+      frame.SetPixelsChanged(true);
+      if (FrameIsReceivedAtIndex(index) || IsAllDataReceived()) {
+        SetFailed();
+      }
+      break;
+    default:
       SetFailed();
-    } else {
-      DecodeSingleFrame(webp_frame.fragment.bytes, webp_frame.fragment.size,
-                        *i);
-      WebPDemuxReleaseIterator(&webp_frame);
-    }
-    if (Failed())
       return;
-
-    // If this returns false, we need more data to continue decoding.
-    if (!PostDecodeProcessing(*i))
-      break;
   }
-
-  // It is also a fatal error if all data is received and we have decoded all
-  // frames available but the file is truncated.
-  if (index >= frame_buffer_cache_.size() - 1 && IsAllDataReceived() &&
-      demux_ && demux_state_ != WEBP_DEMUX_DONE)
-    SetFailed();
 }
 
-bool WEBPImageDecoder::DecodeSingleFrame(const uint8_t* data_bytes,
-                                         size_t data_size,
-                                         size_t frame_index) {
-  if (Failed())
-    return false;
-
-  DCHECK(IsDecodedSizeAvailable());
-
-  DCHECK_GT(frame_buffer_cache_.size(), frame_index);
-  ImageFrame& buffer = frame_buffer_cache_[frame_index];
-  DCHECK_NE(buffer.GetStatus(), ImageFrame::kFrameComplete);
-
-  if (buffer.GetStatus() == ImageFrame::kFrameEmpty) {
-    if (!buffer.AllocatePixelData(Size().Width(), Size().Height(),
-                                  ColorSpaceForSkImages()))
-      return SetFailed();
-    buffer.ZeroFillPixelData();
-    buffer.SetStatus(ImageFrame::kFramePartial);
-    // The buffer is transparent outside the decoded area while the image is
-    // loading. The correct alpha value for the frame will be set when it is
-    // fully decoded.
-    buffer.SetHasAlpha(true);
-    buffer.SetOriginalFrameRect(IntRect(IntPoint(), Size()));
-  }
-
-  const IntRect& frame_rect = buffer.OriginalFrameRect();
-  if (!decoder_) {
-    WEBP_CSP_MODE mode = outputMode(format_flags_ & ALPHA_FLAG);
-    if (!premultiply_alpha_)
-      mode = outputMode(false);
-    if (ColorTransform()) {
-      // Swizzling between RGBA and BGRA is zero cost in a color transform.
-      // So when we have a color transform, we should decode to whatever is
-      // easiest for libwebp, and then let the color transform swizzle if
-      // necessary.
-      // Lossy webp is encoded as YUV (so RGBA and BGRA are the same cost).
-      // Lossless webp is encoded as BGRA. This means decoding to BGRA is
-      // either faster or the same cost as RGBA.
-      mode = MODE_BGRA;
+size_t WEBPImageDecoder::GetViableReferenceFrameIndex(
+    size_t dependent_index) const {
+  DCHECK_LT(dependent_index, frame_buffer_cache_.size());
+
+  size_t required_previous_frame_index =
+      frame_buffer_cache_[dependent_index].RequiredPreviousFrameIndex();
+
+  // Any frame in the range [|required_previous_frame_index|, |dependent_index|)
+  // can be provided as the prior frame to SkCodec.
+  //
+  // SkCodec sets SkCodec::FrameInfo::fRequiredFrame to the earliest frame which
+  // can be used. This might come up when several frames update the same
+  // subregion. If the same subregion is about to be overwritten, it doesn't
+  // matter which frame in that chain is provided.
+  DCHECK_NE(required_previous_frame_index, kNotFound);
+  // Loop backwards because the frames most likely to be in cache are the most
+  // recent.
+  for (size_t i = dependent_index - 1; i != required_previous_frame_index;
+       i--) {
+    const ImageFrame& frame = frame_buffer_cache_[i];
+
+    if (frame.GetStatus() == ImageFrame::kFrameComplete) {
+      return i;
     }
-    WebPInitDecBuffer(&decoder_buffer_);
-    decoder_buffer_.colorspace = mode;
-    decoder_buffer_.u.RGBA.stride =
-        Size().Width() * sizeof(ImageFrame::PixelData);
-    decoder_buffer_.u.RGBA.size =
-        decoder_buffer_.u.RGBA.stride * frame_rect.Height();
-    decoder_buffer_.is_external_memory = 1;
-    decoder_ = WebPINewDecoder(&decoder_buffer_);
-    if (!decoder_)
-      return SetFailed();
   }
 
-  decoder_buffer_.u.RGBA.rgba = reinterpret_cast<uint8_t*>(
-      buffer.GetAddr(frame_rect.X(), frame_rect.Y()));
-
-  switch (WebPIUpdate(decoder_, data_bytes, data_size)) {
-    case VP8_STATUS_OK:
-      ApplyPostProcessing(frame_index);
-      buffer.SetHasAlpha((format_flags_ & ALPHA_FLAG) ||
-                         frame_background_has_alpha_);
-      buffer.SetStatus(ImageFrame::kFrameComplete);
-      ClearDecoder();
-      return true;
-    case VP8_STATUS_SUSPENDED:
-      if (!IsAllDataReceived() && !FrameIsReceivedAtIndex(frame_index)) {
-        ApplyPostProcessing(frame_index);
-        return false;
-      }
-    // FALLTHROUGH
-    default:
-      Clear();
-      return SetFailed();
-  }
+  return kNotFound;
 }
 
 }  // namespace blink