cc: Update discardable image metadata generation to get PaintImages.

cc/paint/paint_op_buffer.h

Index: cc/paint/paint_op_buffer.h
diff --git a/cc/paint/paint_op_buffer.h b/cc/paint/paint_op_buffer.h
index 714f4ef0f2fd656af7d35aad3d50df82fd10483f..92823a355f7c22cb23f54b17358f976e5d073167 100644
--- a/cc/paint/paint_op_buffer.h
+++ b/cc/paint/paint_op_buffer.h
@@ -9,6 +9,7 @@
 
 #include "base/logging.h"
 #include "base/memory/aligned_memory.h"
+#include "cc/paint/discardable_image_map.h"
 #include "cc/paint/paint_canvas.h"
 #include "cc/paint/paint_export.h"
 #include "cc/paint/paint_flags.h"
@@ -20,7 +21,6 @@
 // See: third_party/skia/src/core/SkLiteDL.h.
 
 namespace cc {
-
 class DisplayItemList;
 
 class CC_PAINT_EXPORT ThreadsafeMatrix : public SkMatrix {