cc: Add image to rect map in DiscardableImageMap.

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 471f7ba6ee479e616621729cf55bee52c1c6b1a4..29ca3889827d1d7d5d32dd482de10943fb0f9290 100644
--- a/cc/playback/raster_source.h
+++ b/cc/playback/raster_source.h
@@ -13,6 +13,7 @@
 #include "base/macros.h"
 #include "cc/base/cc_export.h"
 #include "cc/debug/rendering_stats_instrumentation.h"
+#include "cc/playback/image_id.h"
 #include "cc/playback/recording_source.h"
 #include "skia/ext/analysis_canvas.h"
 #include "third_party/skia/include/core/SkPicture.h"
@@ -107,6 +108,8 @@ class CC_EXPORT RasterSource : public base::RefCountedThreadSafe<RasterSource> {
   // Valid rectangle in which everything is recorded and can be rastered from.
   virtual gfx::Rect RecordedViewport() const;
 
+  gfx::Rect GetRectForImage(ImageId image_id) const;
+
   // Tracing functionality.
   virtual void DidBeginTracing();
   virtual void AsValueInto(base::trace_event::TracedValue* array) const;