Add support to send optimal format as part of ScheduleOverlayPlane

cc/output/overlay_candidate.h

Index: cc/output/overlay_candidate.h
diff --git a/cc/output/overlay_candidate.h b/cc/output/overlay_candidate.h
index 1a73561831dea8fe8614d78b3e16aac64ba17a79..3e15e22b3f0c00c77c6e30e39f8eb84d23fcfe98 100644
--- a/cc/output/overlay_candidate.h
+++ b/cc/output/overlay_candidate.h
@@ -10,6 +10,7 @@
 #include "cc/base/cc_export.h"
 #include "cc/quads/render_pass.h"
 #include "cc/resources/resource_format.h"
+#include "ui/gfx/buffer_types.h"
 #include "ui/gfx/geometry/rect.h"
 #include "ui/gfx/geometry/rect_f.h"
 #include "ui/gfx/geometry/size.h"
@@ -52,6 +53,8 @@ class CC_EXPORT OverlayCandidate {
   gfx::OverlayTransform transform;
   // Format of the buffer to composite.
   ResourceFormat format;
+  // Optimal storage format supported by the platform for this candidate.
+  gfx::BufferFormat storage_format;
   // Size of the resource, in pixels.
   gfx::Size resource_size_in_pixels;
   // Rect on the display to position the overlay to. Implementer must convert
@@ -77,6 +80,8 @@ class CC_EXPORT OverlayCandidate {
   // the strategy so the OverlayProcessor can consider subtracting damage caused
   // by underlay quads.
   bool is_unoccluded;
+  // True if any required scaling needs to be handled before composition.
+  bool handle_scaling;
 
   // To be modified by the implementer if this candidate can go into
   // an overlay.