Reimplement vsync latency UMA to be based on BeginImplFrame rather than BeginMainFrame

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/logging.h"
@@ skipping 308 matching lines @@
 }
 
 void Scheduler::BeginImplFrameWithDeadline(const BeginFrameArgs& args) {
   // The storage for |args| is owned by the missed begin frame task. Therefore
   // save |args| before cancelling the task either here or in the deadline.
   BeginFrameArgs adjusted_args = args;
   // Cancel the missed begin frame task in case the BFS sends a begin frame
   // before the missed frame task runs.
   missed_begin_frame_task_.Cancel();
 
   base::TimeTicks now = Now();

[brianderson, 2017/03/16 19:11:56]

You could re-use this Now() and pass it to BeginImplFrame, which would remove a
syscall per frame.

[stanisc, 2017/03/16 20:45:48]

Done.

 
   // Discard missed begin frames if they are too late.
   if (adjusted_args.type == BeginFrameArgs::MISSED &&
       now > adjusted_args.deadline) {
     SendBeginFrameAck(adjusted_args, kBeginFrameSkipped);
     return;
   }
 
   // Run the previous deadline if any.
   if (state_machine_.begin_impl_frame_state() ==
@@ skipping 126 matching lines @@
 void Scheduler::BeginImplFrame(const BeginFrameArgs& args) {
   DCHECK_EQ(state_machine_.begin_impl_frame_state(),
             SchedulerStateMachine::BEGIN_IMPL_FRAME_STATE_IDLE);
   DCHECK(begin_impl_frame_deadline_task_.IsCancelled());
   DCHECK(state_machine_.HasInitializedCompositorFrameSink());
 
   begin_impl_frame_tracker_.Start(args);
   state_machine_.OnBeginImplFrame(args.source_id, args.sequence_number);
   devtools_instrumentation::DidBeginFrame(layer_tree_host_id_);
   compositor_timing_history_->WillBeginImplFrame(
-      state_machine_.NewActiveTreeLikely());
+      state_machine_.NewActiveTreeLikely(), args.frame_time, args.type);
   client_->WillBeginImplFrame(begin_impl_frame_tracker_.Current());
 
   ProcessScheduledActions();
 }
 
 void Scheduler::ScheduleBeginImplFrameDeadline() {
   // The synchronous compositor does not post a deadline task.
   DCHECK(!settings_.using_synchronous_renderer_compositor);
 
   begin_impl_frame_deadline_task_.Cancel();
@@ skipping 130 matching lines @@
     TRACE_EVENT1(TRACE_DISABLED_BY_DEFAULT("cc.debug.scheduler"),
                  "SchedulerStateMachine", "state", AsValue());
     base::AutoReset<SchedulerStateMachine::Action> mark_inside_action(
         &inside_action_, action);
     switch (action) {
       case SchedulerStateMachine::ACTION_NONE:
         break;
       case SchedulerStateMachine::ACTION_SEND_BEGIN_MAIN_FRAME:
         compositor_timing_history_->WillBeginMainFrame(
             begin_main_frame_args_.on_critical_path,
-            begin_main_frame_args_.frame_time,
-            begin_main_frame_args_.type);
+            begin_main_frame_args_.frame_time);
         state_machine_.WillSendBeginMainFrame();
         // TODO(brianderson): Pass begin_main_frame_args_ directly to client.
         client_->ScheduledActionSendBeginMainFrame(begin_main_frame_args_);
         break;
       case SchedulerStateMachine::ACTION_COMMIT: {
         bool commit_has_no_updates = false;
         state_machine_.WillCommit(commit_has_no_updates);
         client_->ScheduledActionCommit();
         break;
       }
@@ skipping 161 matching lines @@
 }
 
 BeginFrameAck Scheduler::CurrentBeginFrameAckForActiveTree() const {
   return BeginFrameAck(
       begin_main_frame_args_.source_id, begin_main_frame_args_.sequence_number,
       state_machine_.last_begin_frame_sequence_number_active_tree_was_fresh(),
       0, true);
 }
 
 }  // namespace cc