cc: Make OverlayCandidate use gfx::BufferFormat instead of cc::ResourceFormat.

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 e41b62b4bf175a95b4bf93a1149ce49f5c1d2fa9..20d54b8359697f2cdbb3f1e8e99ab38f5108f038 100644
--- a/cc/output/overlay_candidate.cc
+++ b/cc/output/overlay_candidate.cc
@@ -173,7 +173,7 @@ 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),
@@ -206,7 +206,6 @@ bool OverlayCandidate::FromDrawQuad(ResourceProvider* resource_provider,
   candidate->quad_rect_in_target_space =
       MathUtil::MapEnclosingClippedRect(transform, quad->rect);
 
-  candidate->format = RGBA_8888;
   candidate->clip_rect = quad->shared_quad_state->clip_rect;
   candidate->is_clipped = quad->shared_quad_state->is_clipped;
 
@@ -262,11 +261,9 @@ bool OverlayCandidate::FromTextureQuad(ResourceProvider* resource_provider,
                                        OverlayCandidate* candidate) {
   if (!resource_provider->IsOverlayCandidate(quad->resource_id()))
     return false;
-
-  gfx::BufferFormat format =
-      resource_provider->GetBufferFormat(quad->resource_id());
+  candidate->format = resource_provider->GetBufferFormat(quad->resource_id());
   if (std::find(std::begin(kOverlayFormats), std::end(kOverlayFormats),
-                format) == std::end(kOverlayFormats))
+                candidate->format) == std::end(kOverlayFormats))
     return false;
   gfx::OverlayTransform overlay_transform = GetOverlayTransform(
       quad->shared_quad_state->quad_to_target_transform, quad->y_flipped);