cc: Add trace events to track main thread latency mode

cc/scheduler/scheduler.cc

 // Copyright 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/scheduler/scheduler.h"
 
 #include <algorithm>
 #include "base/auto_reset.h"
 #include "base/debug/trace_event.h"
 #include "base/debug/trace_event_argument.h"
@@ skipping 498 matching lines @@
     return;
 
   begin_retro_frame_posted_ = true;
   task_runner_->PostTask(FROM_HERE, begin_retro_frame_closure_);
 }
 
 // BeginImplFrame starts a compositor frame that will wait up until a deadline
 // for a BeginMainFrame+activation to complete before it times out and draws
 // any asynchronous animation and scroll/pinch updates.
 void Scheduler::BeginImplFrame(const BeginFrameArgs& args) {
-  TRACE_EVENT1("cc", "Scheduler::BeginImplFrame", "args", args.AsValue());
+  bool main_thread_is_in_high_latency_mode =
+      state_machine_.MainThreadIsInHighLatencyMode();
+  TRACE_EVENT2("cc",
+               "Scheduler::BeginImplFrame",
+               "args",
+               args.AsValue(),
+               "main_thread_is_high_latency",
+               main_thread_is_in_high_latency_mode);
+  TRACE_COUNTER1(TRACE_DISABLED_BY_DEFAULT("cc.debug.scheduler"),
+                 "MainThreadLatency",
+                 main_thread_is_in_high_latency_mode);
   DCHECK_EQ(state_machine_.begin_impl_frame_state(),
             SchedulerStateMachine::BEGIN_IMPL_FRAME_STATE_IDLE);
   DCHECK(state_machine_.HasInitializedOutputSurface());
 
   advance_commit_state_task_.Cancel();
 
   base::TimeDelta draw_duration_estimate = client_->DrawDurationEstimate();
   begin_impl_frame_args_ = args;
   begin_impl_frame_args_.deadline -= draw_duration_estimate;
 
   if (!state_machine_.impl_latency_takes_priority() &&
-      state_machine_.MainThreadIsInHighLatencyMode() &&
+      main_thread_is_in_high_latency_mode &&
       CanCommitAndActivateBeforeDeadline()) {
     state_machine_.SetSkipNextBeginMainFrameToReduceLatency();
   }
 
   client_->WillBeginImplFrame(begin_impl_frame_args_);
   state_machine_.OnBeginImplFrame(begin_impl_frame_args_);
   devtools_instrumentation::DidBeginFrame(layer_tree_host_id_);
 
   ProcessScheduledActions();
 
@@ skipping 231 matching lines @@
 }
 
 bool Scheduler::IsBeginMainFrameSentOrStarted() const {
   return (state_machine_.commit_state() ==
               SchedulerStateMachine::COMMIT_STATE_BEGIN_MAIN_FRAME_SENT ||
           state_machine_.commit_state() ==
               SchedulerStateMachine::COMMIT_STATE_BEGIN_MAIN_FRAME_STARTED);
 }
 
 }  // namespace cc