Remove redundant reading and writing of data about SharedBuffer.

third_party/WebKit/Source/platform/graphics/DeferredImageDecoder.cpp

Index: third_party/WebKit/Source/platform/graphics/DeferredImageDecoder.cpp
diff --git a/third_party/WebKit/Source/platform/graphics/DeferredImageDecoder.cpp b/third_party/WebKit/Source/platform/graphics/DeferredImageDecoder.cpp
index 11944420d2e5e960756c96732004e4eb94f8684b..e563f918bae4a4432ccd3aab6f68f0df775ec38b 100644
--- a/third_party/WebKit/Source/platform/graphics/DeferredImageDecoder.cpp
+++ b/third_party/WebKit/Source/platform/graphics/DeferredImageDecoder.cpp
@@ -128,15 +128,7 @@ sk_sp<SkImage> DeferredImageDecoder::CreateFrameAtIndex(size_t index) {
 }
 
 PassRefPtr<SharedBuffer> DeferredImageDecoder::Data() {
-  if (!rw_buffer_)
-    return nullptr;
-  sk_sp<SkROBuffer> ro_buffer(rw_buffer_->makeROBufferSnapshot());
-  RefPtr<SharedBuffer> shared_buffer = SharedBuffer::Create();
-  SkROBuffer::Iter it(ro_buffer.get());
-  do {
-    shared_buffer->Append(static_cast<const char*>(it.data()), it.size());
-  } while (it.next());
-  return shared_buffer.Release();
+  return buffer_;
 }
 
 void DeferredImageDecoder::SetData(PassRefPtr<SharedBuffer> data,
@@ -144,28 +136,17 @@ void DeferredImageDecoder::SetData(PassRefPtr<SharedBuffer> data,
   SetDataInternal(std::move(data), all_data_received, true);
 }
 
-void DeferredImageDecoder::SetDataInternal(RefPtr<SharedBuffer> data,
+void DeferredImageDecoder::SetDataInternal(PassRefPtr<SharedBuffer> data,
                                            bool all_data_received,
                                            bool push_data_to_decoder) {
+  buffer_ = std::move(data);
+
   if (actual_decoder_) {
     all_data_received_ = all_data_received;
     if (push_data_to_decoder)
-      actual_decoder_->SetData(data, all_data_received);
+      actual_decoder_->SetData(buffer_, all_data_received);
     PrepareLazyDecodedFrames();
   }
-
-  if (frame_generator_) {
-    if (!rw_buffer_)
-      rw_buffer_ = WTF::WrapUnique(new SkRWBuffer(data->size()));
-
-    const char* segment = 0;
-    for (size_t length = data->GetSomeData(segment, rw_buffer_->size()); length;
-         length = data->GetSomeData(segment, rw_buffer_->size())) {
-      DCHECK_GE(data->size(), rw_buffer_->size() + length);
-      const size_t remaining = data->size() - rw_buffer_->size() - length;
-      rw_buffer_->append(segment, length, remaining);
-    }
-  }
 }
 
 bool DeferredImageDecoder::IsSizeAvailable() {
@@ -316,9 +297,8 @@ sk_sp<SkImage> DeferredImageDecoder::CreateFrameImageAtIndex(
   DCHECK_GT(decoded_size.width(), 0);
   DCHECK_GT(decoded_size.height(), 0);
 
-  sk_sp<SkROBuffer> ro_buffer(rw_buffer_->makeROBufferSnapshot());
-  RefPtr<SegmentReader> segment_reader =
-      SegmentReader::CreateFromSkROBuffer(std::move(ro_buffer));
+  RefPtr<SharedBuffer::ThreadSafeStepper> stepper =
+      buffer_->thread_safe_stepper();
 
   SkImageInfo info = SkImageInfo::MakeN32(
       decoded_size.width(), decoded_size.height(),
@@ -326,8 +306,8 @@ sk_sp<SkImage> DeferredImageDecoder::CreateFrameImageAtIndex(
       color_space_for_sk_images_);
 
   auto generator = WTF::MakeUnique<DecodingImageGenerator>(
-      frame_generator_, info, std::move(segment_reader), all_data_received_,
-      index, frame_data_[index].unique_id_);
+      frame_generator_, info, stepper, all_data_received_, index,
+      frame_data_[index].unique_id_);
   generator->SetCanYUVDecode(can_yuv_decode_);
   sk_sp<SkImage> image = SkImage::MakeFromGenerator(std::move(generator));
   if (!image)