cc: Simplify SetNeedsBeginFrames code in scheduler.

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 286 matching lines @@
                                       begin_impl_frame_args_.deadline);
   int64 intervals = 1 + ((now - timebase) / begin_impl_frame_args_.interval);
   return timebase + (begin_impl_frame_args_.interval * intervals);
 }
 
 base::TimeTicks Scheduler::LastBeginImplFrameTime() {
   return begin_impl_frame_args_.frame_time;
 }
 
 void Scheduler::SetupNextBeginFrameIfNeeded() {
-  if (!task_runner_.get())
-    return;
-
-  if (state_machine_.ShouldSetNeedsBeginFrames(
-          frame_source_->NeedsBeginFrames())) {
-    frame_source_->SetNeedsBeginFrames(state_machine_.BeginFrameNeeded());
-    if (!frame_source_->NeedsBeginFrames()) {
+  // Never call SetNeedsBeginFrames if the frame source already has the right
+  // value.
+  if (frame_source_->NeedsBeginFrames() != state_machine_.BeginFrameNeeded()) {
+    if (state_machine_.BeginFrameNeeded()) {
+      // Call SetNeedsBeginFrames(true) as soon as possible.
+      frame_source_->SetNeedsBeginFrames(true);
+    } else if (state_machine_.begin_impl_frame_state() ==
+               SchedulerStateMachine::BEGIN_IMPL_FRAME_STATE_IDLE) {
+      // Call SetNeedsBeginFrames(false) in between frames only.
+      frame_source_->SetNeedsBeginFrames(false);
       client_->SendBeginMainFrameNotExpectedSoon();
     }
   }
 
-  if (state_machine_.begin_impl_frame_state() ==
-      SchedulerStateMachine::BEGIN_IMPL_FRAME_STATE_INSIDE_DEADLINE) {
-    frame_source_->DidFinishFrame(begin_retro_frame_args_.size());
-  }
-
   PostBeginRetroFrameIfNeeded();
-  SetupPollingMechanisms();
 }
 
 // We may need to poll when we can't rely on BeginFrame to advance certain
 // state or to avoid deadlock.
 void Scheduler::SetupPollingMechanisms() {
   bool needs_advance_commit_state_timer = false;
   // Setup PollForAnticipatedDrawTriggers if we need to monitor state but
   // aren't expecting any more BeginFrames. This should only be needed by
   // the synchronous compositor when BeginFrameNeeded is false.
   if (state_machine_.ShouldPollForAnticipatedDrawTriggers()) {
@@ skipping 298 matching lines @@
       FROM_HERE_WITH_EXPLICIT_FUNCTION(
           "461509 Scheduler::OnBeginImplFrameDeadline2"));
   state_machine_.OnBeginImplFrameIdle();
   ProcessScheduledActions();
 
   // TODO(robliao): Remove ScopedTracker below once crbug.com/461509 is fixed.
   tracked_objects::ScopedTracker tracking_profile3(
       FROM_HERE_WITH_EXPLICIT_FUNCTION(
           "461509 Scheduler::OnBeginImplFrameDeadline3"));
   client_->DidBeginImplFrameDeadline();
+  frame_source_->DidFinishFrame(begin_retro_frame_args_.size());
 }
 
 void Scheduler::PollForAnticipatedDrawTriggers() {
   TRACE_EVENT0("cc", "Scheduler::PollForAnticipatedDrawTriggers");
   poll_for_draw_triggers_task_.Cancel();
   state_machine_.DidEnterPollForAnticipatedDrawTriggers();
   ProcessScheduledActions();
   state_machine_.DidLeavePollForAnticipatedDrawTriggers();
 }
 
@@ skipping 120 matching lines @@
         client_->ScheduledActionPrepareTiles();
         break;
       }
     }
   } while (action != SchedulerStateMachine::ACTION_NONE);
 
   // TODO(robliao): Remove ScopedTracker below once crbug.com/461509 is fixed.
   tracked_objects::ScopedTracker tracking_profile10(
       FROM_HERE_WITH_EXPLICIT_FUNCTION(
           "461509 Scheduler::ProcessScheduledActions10"));
-  SetupNextBeginFrameIfNeeded();
+
+  SetupPollingMechanisms();
+
   client_->DidAnticipatedDrawTimeChange(AnticipatedDrawTime());
 
   // TODO(robliao): Remove ScopedTracker below once crbug.com/461509 is fixed.
   tracked_objects::ScopedTracker tracking_profile11(
       FROM_HERE_WITH_EXPLICIT_FUNCTION(
           "461509 Scheduler::ProcessScheduledActions11"));
+
   RescheduleBeginImplFrameDeadlineIfNeeded();
+
+  SetupNextBeginFrameIfNeeded();
 }
 
 scoped_refptr<base::trace_event::ConvertableToTraceFormat> Scheduler::AsValue()
     const {
   scoped_refptr<base::trace_event::TracedValue> state =
       new base::trace_event::TracedValue();
   AsValueInto(state.get());
   return state;
 }
 
@@ skipping 67 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