Revert of Revert of Implement DisplayList GatherPixelRefs

cc/resources/display_list_raster_source.cc

 // Copyright 2014 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/display_list_raster_source.h"
 
 #include "base/trace_event/trace_event.h"
 #include "cc/base/region.h"
 #include "cc/debug/debug_colors.h"
 #include "cc/resources/display_item_list.h"
@@ skipping 141 matching lines @@
   layer_rect.Intersect(gfx::Rect(size_));
   skia::AnalysisCanvas canvas(layer_rect.width(), layer_rect.height());
   RasterForAnalysis(&canvas, layer_rect, 1.0f);
   analysis->is_solid_color = canvas.GetColorIfSolid(&analysis->solid_color);
 }
 
 void DisplayListRasterSource::GatherPixelRefs(
     const gfx::Rect& content_rect,
     float contents_scale,
     std::vector<SkPixelRef*>* pixel_refs) const {
-  // TODO(ajuma): Implement this.
+  DCHECK_EQ(0u, pixel_refs->size());
+
+  gfx::Rect layer_rect =
+      gfx::ScaleToEnclosingRect(content_rect, 1.0f / contents_scale);
+
+  PixelRefMap::Iterator iterator(layer_rect, display_list_.get());
+  while (iterator) {
+    pixel_refs->push_back(*iterator);
+    ++iterator;
+  }
 }
 
 bool DisplayListRasterSource::CoversRect(const gfx::Rect& content_rect,
                                          float contents_scale) const {
   if (size_.IsEmpty())
     return false;
   gfx::Rect layer_rect =
       gfx::ScaleToEnclosingRect(content_rect, 1.f / contents_scale);
   layer_rect.Intersect(gfx::Rect(size_));
 
@@ skipping 41 matching lines @@
 }
 
 scoped_refptr<RasterSource> DisplayListRasterSource::CreateCloneWithoutLCDText()
     const {
   bool can_use_lcd_text = false;
   return scoped_refptr<RasterSource>(
       new DisplayListRasterSource(this, can_use_lcd_text));
 }
 
 }  // namespace cc