Raster PictureLayerTiling with fractional translation

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 e4da161c5382fb47f45fa74e80f49fd4e36883e4..6e2feb8d805d765ce7b77c31dbe6bed27a692c3b 100644
--- a/cc/playback/raster_source.h
+++ b/cc/playback/raster_source.h
@@ -21,6 +21,7 @@ namespace cc {
 class DisplayItemList;
 class DrawImage;
 class ImageDecodeController;
+class ScaleTranslate2d;
 
 class CC_EXPORT RasterSource : public base::RefCountedThreadSafe<RasterSource> {
  public:
@@ -43,11 +44,18 @@ class CC_EXPORT RasterSource : public base::RefCountedThreadSafe<RasterSource> {
       const RecordingSource* other,
       bool can_use_lcd_text);
 
-  // TODO(trchen): Deprecated.
+  // Helper function to apply a few common operations before passing the canvas
+  // to the shorter version. This is useful for rastering into tiles.
+  // canvas is expected to be backed by a tile, with a default state.
+  // contents_transform will be applied to the display list, rastering the list
+  // into the "content space".
+  // canvas_bitmap_rect defines the extent of the tile in the content space,
+  // i.e. contents in the rect will be cropped and translated onto the canvas.
+  // canvas_playback_rect defines the damange rect in the content space.

[enne (OOO), 2016/08/29 20:21:19]

It's true that the canvas_playback_rect is the damage rect, but for the purposes
of this function I think it's better to define it as the subset of the recording
that should be rastered.

   void PlaybackToCanvas(SkCanvas* canvas,
                         const gfx::Rect& canvas_bitmap_rect,
                         const gfx::Rect& canvas_playback_rect,
-                        float contents_scale,
+                        const ScaleTranslate2d& contents_transform,
                         const PlaybackSettings& settings) const;
 
   // Raster this RasterSource into the given canvas. Canvas states such as