cc: make resource keep video buffer format for hardware overlay.

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 64ee2a5766822feccf2798c45864f1dfaafdec50..c4d520626422d0477d4984576c984f6a27081869 100644
--- a/cc/output/overlay_candidate.cc
+++ b/cc/output/overlay_candidate.cc
@@ -168,7 +168,7 @@ gfx::OverlayTransform ComposeTransforms(gfx::OverlayTransform delta,
 
 OverlayCandidate::OverlayCandidate()
     : transform(gfx::OVERLAY_TRANSFORM_NONE),
-      format(RGBA_8888),
+      format(gfx::BufferFormat::RGBA_8888),
       uv_rect(0.f, 0.f, 1.f, 1.f),
       is_clipped(false),
       use_output_surface_for_resource(false),
@@ -201,7 +201,7 @@ bool OverlayCandidate::FromDrawQuad(ResourceProvider* resource_provider,
   candidate->quad_rect_in_target_space =
       MathUtil::MapEnclosingClippedRect(transform, quad->rect);
 
-  candidate->format = RGBA_8888;
+  candidate->format = gfx::BufferFormat::RGBA_8888;
   candidate->clip_rect = quad->shared_quad_state->clip_rect;
   candidate->is_clipped = quad->shared_quad_state->is_clipped;