[cc] Adds source_id and sequence_number to BeginFrameArgs.

cc/test/begin_frame_source_test.cc

Index: cc/test/begin_frame_source_test.cc
diff --git a/cc/test/begin_frame_source_test.cc b/cc/test/begin_frame_source_test.cc
index ef1c03394e90f226b190e293228501a08dfcf9a7..997aa99559b2e30a7c1f0a2015e011829e8c7a0d 100644
--- a/cc/test/begin_frame_source_test.cc
+++ b/cc/test/begin_frame_source_test.cc
@@ -35,6 +35,8 @@ const BeginFrameArgs MockBeginFrameObserver::kDefaultBeginFrameArgs =
         FROM_HERE_WITH_EXPLICIT_FUNCTION(
             "MockBeginFrameObserver::kDefaultBeginFrameArgs"),
 #endif
+        0,
+        BeginFrameArgs::kStartingFrameNumber,

[brianderson, 2016/12/15 22:10:33]

Should this be "Invalid" since the rest of the values in the list correspond to
and invalid BeginFrameArgs?

[Eric Seckler, 2016/12/16 17:25:58]

I added a DCHECK to the BeginFrameArgs constructor with field values, which
verifies that the provided sequence_number is valid. I can get rid of it to
allow a "bad" sequence number here if you'd prefer that?

[brianderson, 2016/12/16 17:53:38]

This is okay as is then. Thanks for the explanation.

         -1,
         -1,
         -1);