cc: Make SingleThreadProxy::CompositeImmediately match scheduler path.

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 920dc15495abdb7be32b0ca26eb5abfb37e9cbbe..bf17528f2b7b0a6d3116b091bb0def438ce9e5c2 100644
--- a/cc/trees/single_thread_proxy.cc
+++ b/cc/trees/single_thread_proxy.cc
@@ -45,6 +45,7 @@ SingleThreadProxy::SingleThreadProxy(
       client_(client),
       timing_history_(layer_tree_host->rendering_stats_instrumentation()),
       next_frame_is_newly_committed_frame_(false),
+      inside_impl_frame_(false),
       inside_draw_(false),
       defer_commits_(false),
       animate_requested_(false),
@@ -586,6 +587,7 @@ void SingleThreadProxy::OnDrawForOutputSurface() {
 void SingleThreadProxy::CompositeImmediately(base::TimeTicks frame_begin_time) {
   TRACE_EVENT0("cc,benchmark", "SingleThreadProxy::CompositeImmediately");
   DCHECK(Proxy::IsMainThread());
+  DCHECK(!inside_impl_frame_);
   base::AutoReset<bool> inside_composite(&inside_synchronous_composite_, true);
 
   if (layer_tree_host_->output_surface_lost()) {
@@ -596,10 +598,19 @@ void SingleThreadProxy::CompositeImmediately(base::TimeTicks frame_begin_time) {
       return;
   }
 
+  BeginFrameArgs begin_frame_args(BeginFrameArgs::Create(
+      BEGINFRAME_FROM_HERE, frame_begin_time, base::TimeTicks(),
+      BeginFrameArgs::DefaultInterval(), BeginFrameArgs::NORMAL));
+
+  // Start the impl frame.
+  {
+    DebugScopedSetImplThread impl(const_cast<SingleThreadProxy*>(this));

[sunnyps, 2015/05/01 00:46:38]

Why do you need a const_cast here? 'this' is not const in a non-const method,
right? If this is not needed, can you change the other uses of const_cast in
this method too?

[mithro-old, 2015/05/01 03:08:54]

Done.

+    WillBeginImplFrame(begin_frame_args);
+  }
+
+  // Run the "main thread" and get it to commit.
   {
-    BeginFrameArgs begin_frame_args(BeginFrameArgs::Create(
-        BEGINFRAME_FROM_HERE, frame_begin_time, base::TimeTicks(),
-        BeginFrameArgs::DefaultInterval(), BeginFrameArgs::NORMAL));
+    DCHECK(inside_impl_frame_);

[sunnyps, 2015/05/01 00:46:38]

nit: move this DCHECK to immediately under the WillBeginImplFrame.

[mithro-old, 2015/05/01 03:08:54]

This DCHCEK is checking that when you call DoBeginMainFrame we are inside an
impl frame. This means it should be logically in the same scope as the
DoBeginMainFrame (IE if you were to split the stuff out into it's own function
then you'd take the DCHECK with it).

     DoBeginMainFrame(begin_frame_args);
     DoCommit();
 
@@ -607,6 +618,7 @@ void SingleThreadProxy::CompositeImmediately(base::TimeTicks frame_begin_time) {
         << "Commit should always succeed and transfer promises.";
   }
 
+  // Finish the impl frame.
   {
     DebugScopedSetImplThread impl(const_cast<SingleThreadProxy*>(this));
     if (layer_tree_host_impl_->settings().impl_side_painting) {
@@ -626,6 +638,8 @@ void SingleThreadProxy::CompositeImmediately(base::TimeTicks frame_begin_time) {
     // another draw will never be scheduled, so break remaining promises.
     layer_tree_host_impl_->active_tree()->BreakSwapPromises(
         SwapPromise::SWAP_FAILS);
+
+    DidBeginImplFrameDeadline();
   }
 }
 
@@ -716,12 +730,6 @@ DrawResult SingleThreadProxy::DoComposite(base::TimeTicks frame_begin_time,
         FROM_HERE_WITH_EXPLICIT_FUNCTION(
             "461509 SingleThreadProxy::DoComposite5"));
     layer_tree_host_impl_->UpdateAnimationState(start_ready_animations);
-    // TODO(robliao): Remove ScopedTracker below once https://crbug.com/461509
-    // is fixed.
-    tracked_objects::ScopedTracker tracking_profile6(

[sunnyps, 2015/05/01 00:46:38]

This is related to the other CL right?
https://codereview.chromium.org/1111743002/

[mithro-old, 2015/05/01 03:08:55]

Yes, this patch is dependent on that CL. I uploaded it to test on the try bots,
you should be looking at patchset #3 ->
https://codereview.chromium.org/1099703004/#ps40001

Reitveld / Commit Queue doesn't deal with dependent patches :(

-        FROM_HERE_WITH_EXPLICIT_FUNCTION(
-            "461509 SingleThreadProxy::DoComposite6"));
-    layer_tree_host_impl_->ResetCurrentBeginFrameArgsForNextFrame();
 
     // TODO(robliao): Remove ScopedTracker below once https://crbug.com/461509
     // is fixed.
@@ -791,6 +799,9 @@ void SingleThreadProxy::SetAuthoritativeVSyncInterval(
 }
 
 void SingleThreadProxy::WillBeginImplFrame(const BeginFrameArgs& args) {
+  DCHECK(!inside_impl_frame_)
+      << "WillBeginImplFrame called while already inside an impl frame!";
+  inside_impl_frame_ = true;
   layer_tree_host_impl_->WillBeginImplFrame(args);
 }
 
@@ -803,17 +814,21 @@ void SingleThreadProxy::ScheduledActionSendBeginMainFrame() {
   // fall on the next.  Doing it asynchronously instead matches the semantics of
   // ThreadProxy::SetNeedsCommit where SetNeedsCommit will not cause a
   // synchronous commit.
+  DCHECK(inside_impl_frame_)

[sunnyps, 2015/05/01 00:46:38]

We're pretty sure this is true for SingleThreadProxy, right?

[mithro-old, 2015/05/01 03:08:54]

We'd hope so, but as SRE says "hope is not a strategy" so we check. Then when
someone breaks the assumption this will fail before they commit it.

+      << "BeginMainFrame should only be sent inside a BeginImplFrame";
+  const BeginFrameArgs& begin_frame_args =
+      layer_tree_host_impl_->CurrentBeginFrameArgs();
+
   MainThreadTaskRunner()->PostTask(
-      FROM_HERE,
-      base::Bind(&SingleThreadProxy::BeginMainFrame,
-                 weak_factory_.GetWeakPtr()));
+      FROM_HERE, base::Bind(&SingleThreadProxy::BeginMainFrame,
+                            weak_factory_.GetWeakPtr(), begin_frame_args));
 }
 
 void SingleThreadProxy::SendBeginMainFrameNotExpectedSoon() {
   layer_tree_host_->BeginMainFrameNotExpectedSoon();
 }
 
-void SingleThreadProxy::BeginMainFrame() {
+void SingleThreadProxy::BeginMainFrame(const BeginFrameArgs& begin_frame_args) {
   commit_requested_ = false;
   animate_requested_ = false;
 
@@ -849,8 +864,6 @@ void SingleThreadProxy::BeginMainFrame() {
   // a commit here.
   commit_requested_ = true;
 
-  const BeginFrameArgs& begin_frame_args =
-      layer_tree_host_impl_->CurrentBeginFrameArgs();
   DoBeginMainFrame(begin_frame_args);
 }
 
@@ -969,6 +982,9 @@ base::TimeDelta SingleThreadProxy::CommitToActivateDurationEstimate() {
 
 void SingleThreadProxy::DidBeginImplFrameDeadline() {
   layer_tree_host_impl_->ResetCurrentBeginFrameArgsForNextFrame();
+  DCHECK(inside_impl_frame_)
+      << "DidBeginImplFrameDeadline called while not inside an impl frame!";
+  inside_impl_frame_ = false;
 }
 
 void SingleThreadProxy::SendBeginFramesToChildren(const BeginFrameArgs& args) {