[cc] Add and use BeginFrameAck for DidFinishFrame.

cc/ipc/begin_frame_args_struct_traits.h

Index: cc/ipc/begin_frame_args_struct_traits.h
diff --git a/cc/ipc/begin_frame_args_struct_traits.h b/cc/ipc/begin_frame_args_struct_traits.h
index 4d813395c282743b2c57f38985b3572113db3993..b189414b3b72af14914cf5e8efb2a5928e8cfc1b 100644
--- a/cc/ipc/begin_frame_args_struct_traits.h
+++ b/cc/ipc/begin_frame_args_struct_traits.h
@@ -56,6 +56,41 @@ struct StructTraits<cc::mojom::BeginFrameArgsDataView, cc::BeginFrameArgs> {
   }
 };
 
+template <>
+struct StructTraits<cc::mojom::BeginFrameAckDataView, cc::BeginFrameAck> {
+  static uint64_t sequence_number(const cc::BeginFrameAck& ack) {
+    return ack.sequence_number;
+  }
+
+  static uint64_t latest_confirmed_sequence_number(
+      const cc::BeginFrameAck& ack) {
+    return ack.latest_confirmed_sequence_number;
+  }
+
+  static uint32_t source_id(const cc::BeginFrameAck& ack) {
+    return ack.source_id;
+  }
+
+  static uint32_t remaining_frames(const cc::BeginFrameAck& ack) {
+    return ack.remaining_frames;
+  }
+
+  static bool has_damage(const cc::BeginFrameAck& ack) {
+    return ack.has_damage;
+  }
+
+  static bool Read(cc::mojom::BeginFrameAckDataView data,
+                   cc::BeginFrameAck* out) {

[dcheng, 2017/01/05 06:49:54]

Nit: Read() methods should generally out-of-lined, can we do that here?

[Eric Seckler, 2017/01/06 16:08:51]

will do when we add it back in a later CL :)

+    out->source_id = data.source_id();
+    out->sequence_number = data.sequence_number();
+    out->latest_confirmed_sequence_number =
+        data.latest_confirmed_sequence_number();
+    out->remaining_frames = data.remaining_frames();
+    out->has_damage = data.has_damage();
+    return true;
+  }
+};
+
 }  // namespace mojo
 
 #endif  // CC_IPC_BEGIN_FRAME_ARGS_STRUCT_TRAITS_H_