[SkiaBenchmarkingExtension] Add draw command timing info.

content/renderer/skia_benchmarking/skia_benchmarking_canvas.h

+// Copyright (c) 2013 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.
+
+#ifndef CONTENT_RENDERER_SKIA_BENCHMARKING_CANVAS_H_
+#define CONTENT_RENDERER_SKIA_BENCHMARKING_CANVAS_H_
+
+#include "base/compiler_specific.h"
+#include "base/memory/ref_counted.h"
+#include "third_party/skia/include/utils/SkNWayCanvas.h"
+#include "third_party/skia/src/utils/debugger/SkDebugCanvas.h"
+
+namespace gfx {
+class Rect;
+}
+
+namespace content {
+
+class SkiaTimingCanvas;
+
+class SkiaBenchmarkingCanvas : public SkNWayCanvas {
+public:
+  SkiaBenchmarkingCanvas(const gfx::Rect&);
+  virtual ~SkiaBenchmarkingCanvas();
+
+  // Returns the number of draw commands executed on this canvas.
+  size_t CommandCount() const;
+
+  // Get draw command info for a given index.
+  SkDrawCommand* GetCommand(size_t index);
+
+  // Return the recorded render time (microseconds) for a draw command index.
+  int64 GetTime(size_t index);
+
+private:
+  // In order to avoid introducing a Skia version dependency, this
+  // implementation dispatches draw commands in lock-step to two distinct
+  // canvases:
+  //   * a SkDebugCanvas used for gathering command info and tracking
+  //     the current command index
+  //   * a SkiaTimingCanvas used for measuring raster paint times (and relying
+  //     on the former for tracking the current command index).
+  //
+  // This way, if the SkCanvas API is extended, we don't need to worry about
+  // updating content::SkiaTimingCanvas to accurately override all new methods
+  // (to avoid timing info indices from getting out of sync), as SkDebugCanvas
+  // already does that for us.
+
+  scoped_refptr<SkDebugCanvas> debug_canvas_;
+  scoped_refptr<SkiaTimingCanvas> timing_canvas_;
+};
+
+}
+#endif // CONTENT_RENDERER_SKIA_BENCHMARKING_CANVAS_H