Skip clearing the canvas before painting the contents of opaque layers

cc/resources/skpicture_content_layer_updater.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/resources/skpicture_content_layer_updater.h"
 
 #include "base/debug/trace_event.h"
 #include "cc/debug/rendering_stats_instrumentation.h"
 #include "cc/resources/layer_painter.h"
 #include "cc/resources/prioritized_resource.h"
 #include "cc/resources/resource_update_queue.h"
 #include "third_party/skia/include/core/SkCanvas.h"
 
 namespace cc {
 
 SkPictureContentLayerUpdater::SkPictureContentLayerUpdater(
     scoped_ptr<LayerPainter> painter,
     RenderingStatsInstrumentation* stats_instrumentation,
     int layer_id)
-    : ContentLayerUpdater(painter.Pass(), stats_instrumentation, layer_id),
-      layer_is_opaque_(false) {}
+    : ContentLayerUpdater(painter.Pass(), stats_instrumentation, layer_id) {}
 
 SkPictureContentLayerUpdater::~SkPictureContentLayerUpdater() {}
 
 void SkPictureContentLayerUpdater::PrepareToUpdate(
     gfx::Rect content_rect,
     gfx::Size,
     float contents_width_scale,
     float contents_height_scale,
     gfx::Rect* resulting_opaque_rect) {
   SkCanvas* canvas =
       picture_.beginRecording(content_rect.width(), content_rect.height());
   base::TimeTicks start_time =
       rendering_stats_instrumentation_->StartRecording();
   PaintContents(canvas,
-                content_rect,
+                content_rect.origin(),
                 contents_width_scale,
                 contents_height_scale,
                 resulting_opaque_rect);
   base::TimeDelta duration =
       rendering_stats_instrumentation_->EndRecording(start_time);
   rendering_stats_instrumentation_->AddRecord(
       duration, content_rect.width() * content_rect.height());
   picture_.endRecording();
 }
 
 void SkPictureContentLayerUpdater::DrawPicture(SkCanvas* canvas) {
   TRACE_EVENT0("cc", "SkPictureContentLayerUpdater::DrawPicture");
   canvas->drawPicture(picture_);
 }
 
-void SkPictureContentLayerUpdater::SetOpaque(bool opaque) {
-  layer_is_opaque_ = opaque;
-}
-
 }  // namespace cc