cc: Do the math for a tile's content rect in layer space once.

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 869ad93900ea664f9f1b1b737315b368fbafbe16..0ff0d546487281f614e46e22aa858a53a99d798b 100644
--- a/cc/playback/raster_source.h
+++ b/cc/playback/raster_source.h
@@ -71,16 +71,14 @@ class CC_EXPORT RasterSource : public base::RefCountedThreadSafe<RasterSource> {
   virtual gfx::Size GetSize() const = 0;
 
   // Populate the given list with all SkPixelRefs that may overlap the given
-  // rect at given scale.
+  // rect in layer space.
   virtual void GatherPixelRefs(
-      const gfx::Rect& content_rect,
-      float contents_scale,
+      const gfx::Rect& layer_rect,
       std::vector<skia::PositionPixelRef>* pixel_refs) const = 0;
 
-  // Return true iff this raster source can raster the given rect at given
-  // scale.
-  virtual bool CoversRect(const gfx::Rect& content_rect,
-                          float contents_scale) const = 0;
+  // Return true iff this raster source can raster the given rect in layer
+  // space.
+  virtual bool CoversRect(const gfx::Rect& layer_rect) const = 0;
 
   // Returns true if this raster source has anything to rasterize.
   virtual bool HasRecordings() const = 0;