cc: Introduce BeginFrame sequence numbers and acknowledgements.

cc/trees/single_thread_proxy.cc

Index: cc/trees/single_thread_proxy.cc
diff --git a/cc/trees/single_thread_proxy.cc b/cc/trees/single_thread_proxy.cc
index 593a7dc06294fd091f695cb336767deee46edc6a..103a77097d233337c8fb0ce2337c5c7ec0a27ae5 100644
--- a/cc/trees/single_thread_proxy.cc
+++ b/cc/trees/single_thread_proxy.cc
@@ -450,7 +450,7 @@ void SingleThreadProxy::CompositeImmediately(base::TimeTicks frame_begin_time) {
   }
 
   BeginFrameArgs begin_frame_args(BeginFrameArgs::Create(
-      BEGINFRAME_FROM_HERE, frame_begin_time, base::TimeTicks(),
+      BEGINFRAME_FROM_HERE, 0, 1, frame_begin_time, base::TimeTicks(),
       BeginFrameArgs::DefaultInterval(), BeginFrameArgs::NORMAL));
 
   // Start the impl frame.
@@ -486,6 +486,9 @@ void SingleThreadProxy::CompositeImmediately(base::TimeTicks frame_begin_time) {
     layer_tree_host_impl_->Animate();
 
     LayerTreeHostImpl::FrameData frame;
+    frame.begin_frame_source_id = 0;
+    frame.begin_frame_number = 1;
+    frame.latest_confirmed_frame = 1;
     DoComposite(&frame);
 
     // DoComposite could abort, but because this is a synchronous composite
@@ -692,6 +695,12 @@ void SingleThreadProxy::BeginMainFrameAbortedOnImplThread(
 DrawResult SingleThreadProxy::ScheduledActionDrawIfPossible() {
   DebugScopedSetImplThread impl(task_runner_provider_);
   LayerTreeHostImpl::FrameData frame;
+  frame.begin_frame_source_id =
+      scheduler_on_impl_thread_->CurrentBeginFrameSourceId();
+  frame.begin_frame_number =
+      scheduler_on_impl_thread_->CurrentBeginFrameNumber();
+  frame.latest_confirmed_frame =
+      scheduler_on_impl_thread_->LatestConfirmedFrameForActiveTree();
   return DoComposite(&frame);
 }