cc: Introduce BeginFrame sequence numbers and acknowledgements.

cc/test/fake_external_begin_frame_source.cc

Index: cc/test/fake_external_begin_frame_source.cc
diff --git a/cc/test/fake_external_begin_frame_source.cc b/cc/test/fake_external_begin_frame_source.cc
index 1a15b09b49ab69a2aa0a9233efe04493147cff3b..c332b4d1f22e92907587f7e5c7918f6729f43418 100644
--- a/cc/test/fake_external_begin_frame_source.cc
+++ b/cc/test/fake_external_begin_frame_source.cc
@@ -77,9 +77,10 @@ void FakeExternalBeginFrameSource::PostTestOnBeginFrame() {
       base::Bind(&FakeExternalBeginFrameSource::TestOnBeginFrame,
                  weak_ptr_factory_.GetWeakPtr()));
   base::ThreadTaskRunnerHandle::Get()->PostDelayedTask(
-      FROM_HERE,
-      base::Bind(begin_frame_task_.callback(),
-                 CreateBeginFrameArgsForTesting(BEGINFRAME_FROM_HERE)),
+      FROM_HERE, base::Bind(begin_frame_task_.callback(),
+                            CreateBeginFrameArgsForTesting(
+                                BEGINFRAME_FROM_HERE, source_id(),
+                                next_begin_frame_number_++)),
       base::TimeDelta::FromMilliseconds(milliseconds_per_frame_));
 }