cc: Add image decode control in the compositor.

cc/playback/discardable_image_map.h

Index: cc/playback/discardable_image_map.h
diff --git a/cc/playback/discardable_image_map.h b/cc/playback/discardable_image_map.h
index 0306e1b7e526bf1e2e1648766f90a3b309413281..47cbe20ab60fb0f9bd8492e4d648a1d4b9d16d99 100644
--- a/cc/playback/discardable_image_map.h
+++ b/cc/playback/discardable_image_map.h
@@ -20,6 +20,21 @@ class SkImage;
 
 namespace cc {
 
+// Helper function to apply the matrix to the rect and return the result.
+SkRect MapRect(const SkMatrix& matrix, const SkRect& src);
+
+// Helper funciton to extract a scale from the matrix. Returns true on success
+// and false on failure.
+bool ExtractScale(const SkMatrix& matrix, SkSize* scale);
+
+// Helper function to compute the new rect bounds adjusted for both the current
+// paint and all of the saved paints. Returns true on success and false on
+// failure.
+bool ComputeRectBoundsFromPaint(const SkRect& rect,
+                                const SkPaint* current_paint,
+                                const std::vector<const SkPaint*>& saved_paints,
+                                SkRect* paint_bounds);
+
 // This class is used for generating discardable images data (see DrawImage
 // for the type of data it stores). It allows the client to query a particular
 // rect and get back a list of DrawImages in that rect.