[cc] Set BeginFrame sequence numbers on CompositorFrames from Scheduler.

cc/output/compositor_frame_metadata.h

Index: cc/output/compositor_frame_metadata.h
diff --git a/cc/output/compositor_frame_metadata.h b/cc/output/compositor_frame_metadata.h
index e383e5069dcd82c0f9c4a044fd4f38d6eabc4969..53906913a2669092664123a453bbd17686b93e1e 100644
--- a/cc/output/compositor_frame_metadata.h
+++ b/cc/output/compositor_frame_metadata.h
@@ -11,6 +11,7 @@
 
 #include "cc/base/cc_export.h"
 #include "cc/input/selection.h"
+#include "cc/output/begin_frame_args.h"
 #include "cc/surfaces/surface_id.h"
 #include "third_party/skia/include/core/SkColor.h"
 #include "ui/events/latency_info.h"
@@ -82,6 +83,13 @@ class CC_EXPORT CompositorFrameMetadata {
   // dependencies have been resolved.
   bool can_activate_before_dependencies = true;
 
+  // Source identifier and sequence number of the BeginFrame that this
+  // CompositorFrame is in response to and sequence number that it confirms.
+  uint32_t begin_frame_source_id = 0;
+  uint64_t begin_frame_sequence_number = BeginFrameArgs::kInvalidFrameNumber;
+  uint64_t latest_confirmed_begin_frame_sequence_number =
+      BeginFrameArgs::kInvalidFrameNumber;

[brianderson, 2017/02/24 01:08:36]

Can this be an instance of the BeginFrameAck struct?

[Eric Seckler, 2017/02/27 11:50:32]

Done. Was trying to avoid overhead of the unused fields (remaining_frames and
has_damage), but it does look nicer having an ACK in here, and the overhead
should be minimal. And remaining_frames should go away eventually.

+
  private:
   CompositorFrameMetadata(const CompositorFrameMetadata& other);
   CompositorFrameMetadata operator=(const CompositorFrameMetadata&) = delete;