Plumb activation time to main

cc/output/begin_frame_args.h

Index: cc/output/begin_frame_args.h
diff --git a/cc/output/begin_frame_args.h b/cc/output/begin_frame_args.h
index d4ced74a32c9bac8c462864f32e6b815151b8962..ff2ee5a56ba5f5a973cac1b9fea8106dc87dfb55 100644
--- a/cc/output/begin_frame_args.h
+++ b/cc/output/begin_frame_args.h
@@ -61,6 +61,7 @@ struct CC_EXPORT BeginFrameArgs {
 
   // Creates an invalid set of values.
   BeginFrameArgs();
+  ~BeginFrameArgs();
 
 #ifdef NDEBUG
   typedef const void* CreationLocation;
@@ -79,6 +80,7 @@ struct CC_EXPORT BeginFrameArgs {
                                base::TimeTicks deadline,
                                base::TimeDelta interval,
                                BeginFrameArgsType type);
+  BeginFrameArgs(const BeginFrameArgs&);
 
   // This is the default delta that will be used to adjust the deadline when
   // proper draw-time estimations are not yet available.
@@ -103,6 +105,10 @@ struct CC_EXPORT BeginFrameArgs {
   // observers should expect the continuity of |sequence_number| to break.
   uint64_t sequence_number;
   uint32_t source_id;  // |source_id| after |sequence_number| for packing.
+  uint32_t frame_source_number;

[vmpstr, 2017/04/05 19:11:33]

nit: source_frame_number to be consistent with the rest of the places

[brianderson, 2017/04/06 23:43:15]

A few comments:

* Make sure to initialize this in each of the constructors.

* Add a comment like:
"|source_frame_number| is set by the LayerTreeHost when the BeginFrame reaches
blink and corresponds to the commit count."

* "source" in this context is overloaded since it could correspond to the
BeginFrameSource. Maybe rename it to "commit_number" so it's more obvious it
relates to the commit. Although, I do still have a preference for a separate
BeginMainFrameArgs which would also avoid overloading the "source" concept.

[panicker, 2017/04/08 00:29:06]

Updated.
Happy to try out the BeginMainFrameArgs subsclassing as a follow up change, if
that's fine with you. Otherwise it's adding not necessary complexity to this
change.

+
+  // This is to report Activation time back to main.

[vmpstr, 2017/04/05 19:11:33]

Can you please elaborate on this comment a bit. Specifically, what the pair
represents and why it's a vector as opposed to a single value?

[panicker, 2017/04/08 00:29:06]

Done.

+  std::vector<std::pair<uint32_t, base::TimeTicks>> ready_to_activate_time;
 
   BeginFrameArgsType type;
   bool on_critical_path;