Extract subpixel offsets from composited layer transforms when possible.

cc/playback/raster_source.h

Index: cc/playback/raster_source.h
diff --git a/cc/playback/raster_source.h b/cc/playback/raster_source.h
index 062316ca2a31dd5c507317934d8e5cdc87514c04..368c4273f3ddcae3cf82f9133e1bdc00aa90f317 100644
--- a/cc/playback/raster_source.h
+++ b/cc/playback/raster_source.h
@@ -19,6 +19,7 @@
 #include "cc/playback/display_list_recording_source.h"
 #include "skia/ext/analysis_canvas.h"
 #include "third_party/skia/include/core/SkPicture.h"
+#include "ui/gfx/geometry/vector2d_f.h"
 
 namespace cc {
 class DisplayItemList;
@@ -63,6 +64,8 @@ class CC_EXPORT RasterSource : public base::trace_event::MemoryDumpProvider,
                                  float contents_scale,
                                  SkColor* color) const;
 
+  void SetSubpixelOffset(const gfx::Vector2dF& subpixel_offset) { subpixel_offset_ = subpixel_offset; }
+
   // Returns true iff the whole raster source is of solid color.
   bool IsSolidColor() const;
 
@@ -166,6 +169,8 @@ class CC_EXPORT RasterSource : public base::trace_event::MemoryDumpProvider,
   // Used to ensure that memory dump logic always happens on the same thread.
   base::ThreadChecker memory_dump_thread_checker_;
 
+  gfx::Vector2dF subpixel_offset_;
+
   DISALLOW_COPY_AND_ASSIGN(RasterSource);
 };