cc: Include pictures in trace output for DisplayItemLists

cc/resources/drawing_display_item.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/drawing_display_item.h"
 
 #include "third_party/skia/include/core/SkCanvas.h"
 #include "third_party/skia/include/core/SkDrawPictureCallback.h"
 #include "third_party/skia/include/core/SkMatrix.h"
 #include "third_party/skia/include/core/SkPicture.h"
@@ skipping 13 matching lines @@
                                 SkDrawPictureCallback* callback) const {
   canvas->save();
   canvas->translate(location_.x(), location_.y());
   if (callback)
     picture_->playback(canvas, callback);
   else
     canvas->drawPicture(picture_.get());
   canvas->restore();
 }
 
+void DrawingDisplayItem::RasterForTracing(SkCanvas* canvas) const {
+  canvas->save();
+  canvas->translate(location_.x(), location_.y());
+  // The picture debugger in about:tracing doesn't drill down into |drawPicture|
+  // operations. Calling |playback()| rather than |drawPicture()| causes the
+  // skia operations in |picture_| to appear individually in the picture
+  // produced for tracing rather than being hidden inside a drawPicture
+  // operation.
+  picture_->playback(canvas);
+  canvas->restore();
+}
+
 bool DrawingDisplayItem::IsSuitableForGpuRasterization() const {
   return picture_->suitableForGpuRasterization(NULL);
 }
 
 int DrawingDisplayItem::ApproximateOpCount() const {
   return picture_->approximateOpCount() + sizeof(gfx::PointF);
 }
 
 size_t DrawingDisplayItem::PictureMemoryUsage() const {
   DCHECK(picture_);
   return SkPictureUtils::ApproximateBytesUsed(picture_.get());
 }
 
 }  // namespace cc