cc: Move pre-decodes to background worker.

cc/paint/draw_image.h

Index: cc/paint/draw_image.h
diff --git a/cc/paint/draw_image.h b/cc/paint/draw_image.h
index fe84f0606ef34572cf1332ff490c68e02a489a42..8f202b1d6290c7809f68add390fdc55bba1952ca 100644
--- a/cc/paint/draw_image.h
+++ b/cc/paint/draw_image.h
@@ -30,6 +30,8 @@ class CC_PAINT_EXPORT DrawImage {
   DrawImage(const DrawImage& other);
   ~DrawImage();
 
+  bool operator==(const DrawImage& other) const;
+
   const PaintImage& paint_image() const { return paint_image_; }
   const sk_sp<SkImage>& image() const { return paint_image_.sk_image(); }
   const SkSize& scale() const { return scale_; }