Deserialize frame_token in CompositorFrameMetadata's struct traits

In my last CL I added the serialization code but not deserialization.

TBR=danakj@chromium.org
BUG=704972

Review-Url: https://codereview.chromium.org/2801603009
Cr-Commit-Position: refs/heads/master@{#462697}

cc/ipc/compositor_frame_metadata_struct_traits.cc

@@ -38,7 +38,7 @@ bool StructTraits<cc::mojom::CompositorFrameMetadataDataView,
   out->bottom_controls_height = data.bottom_controls_height();
   out->bottom_controls_shown_ratio = data.bottom_controls_shown_ratio();
   out->content_source_id = data.content_source_id();
-
+  out->frame_token = data.frame_token();
   out->root_background_color = data.root_background_color();
   out->can_activate_before_dependencies =
       data.can_activate_before_dependencies();

cc/ipc/struct_traits_unittest.cc

@@ -374,6 +374,7 @@ TEST_F(StructTraitsTest, CompositorFrameMetadata) {
   SurfaceId id(FrameSinkId(1234, 4321),
                LocalSurfaceId(5678, base::UnguessableToken::Create()));
   referenced_surfaces.push_back(id);
+  uint32_t frame_token = 0xdeadbeef;
 
   CompositorFrameMetadata input;
   input.device_scale_factor = device_scale_factor;
@@ -396,6 +397,7 @@ TEST_F(StructTraitsTest, CompositorFrameMetadata) {
   input.selection = selection;
   input.latency_info = latency_infos;
   input.referenced_surfaces = referenced_surfaces;
+  input.frame_token = frame_token;
 
   mojom::TraitsTestServicePtr proxy = GetTraitsTestProxy();
   CompositorFrameMetadata output;
@@ -427,6 +429,7 @@ TEST_F(StructTraitsTest, CompositorFrameMetadata) {
   EXPECT_EQ(referenced_surfaces.size(), output.referenced_surfaces.size());
   for (uint32_t i = 0; i < referenced_surfaces.size(); ++i)
     EXPECT_EQ(referenced_surfaces[i], output.referenced_surfaces[i]);
+  EXPECT_EQ(frame_token, output.frame_token);
 }
 
 TEST_F(StructTraitsTest, CopyOutputRequest_BitmapRequest) {