Add decode() functionality to image elements.

cc/trees/layer_tree_host_impl.cc

 // Copyright 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/trees/layer_tree_host_impl.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <algorithm>
@@ skipping 2326 matching lines @@
   decoded_image_tracker_.QueueImageDecode(
       std::move(image), base::Bind(&LayerTreeHostImpl::ImageDecodeFinished,
                                    base::Unretained(this), embedder_callback));
 }
 
 void LayerTreeHostImpl::ImageDecodeFinished(
     const base::Callback<void(bool)>& embedder_callback,
     bool decode_succeeded) {
   completed_image_decode_callbacks_.emplace_back(
       base::Bind(embedder_callback, decode_succeeded));
-  client_->SetNeedsCommitOnImplThread();
+  client_->NotifyImageDecodeRequestFinished();
 }
 
 std::vector<base::Closure>
 LayerTreeHostImpl::TakeCompletedImageDecodeCallbacks() {
   auto result = std::move(completed_image_decode_callbacks_);
   completed_image_decode_callbacks_.clear();
   return result;
 }
 
 void LayerTreeHostImpl::ClearImageCacheOnNavigation() {
@@ skipping 1945 matching lines @@
 
 void LayerTreeHostImpl::ShowScrollbarsForImplScroll(ElementId element_id) {
   if (!element_id)
     return;
   if (ScrollbarAnimationController* animation_controller =
           ScrollbarAnimationControllerForElementId(element_id))
     animation_controller->DidScrollUpdate();
 }
 
 }  // namespace cc