Add support to send optimal format as part of ScheduleOverlayPlane

cc/output/overlay_candidate.cc

Index: cc/output/overlay_candidate.cc
diff --git a/cc/output/overlay_candidate.cc b/cc/output/overlay_candidate.cc
index 367f31632734613be4394913615192d0fc0f4888..dddfbb598cccc56b92e67e762448fafc1d3d7bd3 100644
--- a/cc/output/overlay_candidate.cc
+++ b/cc/output/overlay_candidate.cc
@@ -170,12 +170,14 @@ gfx::OverlayTransform ComposeTransforms(gfx::OverlayTransform delta,
 OverlayCandidate::OverlayCandidate()
     : transform(gfx::OVERLAY_TRANSFORM_NONE),
       format(RGBA_8888),
+      storage_format(gfx::BufferFormat::BGRX_8888),
       uv_rect(0.f, 0.f, 1.f, 1.f),
       is_clipped(false),
       use_output_surface_for_resource(false),
       resource_id(0),
       plane_z_order(0),
       is_unoccluded(false),
+      handle_scaling(true),
       overlay_handled(false) {}
 
 OverlayCandidate::~OverlayCandidate() {}