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 281 matching lines @@
   base::TimeTicks timebase = std::max(begin_impl_frame_args_.frame_time,
                                       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())
+void Scheduler::SetNeedsBeginFrameIfNeeded() {
+  // Never call SetNeedsBeginFrames if the frame source already has the right
+  // value.
+  if (frame_source_->NeedsBeginFrames() == state_machine_.BeginFrameNeeded())
     return;
 
-  if (state_machine_.ShouldSetNeedsBeginFrames(
-          frame_source_->NeedsBeginFrames())) {
-    frame_source_->SetNeedsBeginFrames(state_machine_.BeginFrameNeeded());
-    if (!frame_source_->NeedsBeginFrames()) {
-      client_->SendBeginMainFrameNotExpectedSoon();
-    }
+  // Always call SetNeedsBeginFrames(true). Only call SetNeedsBeginFrames(false)
+  // in between BeginFrames i.e. when begin_impl_frame_state is IDLE.
+  if (state_machine_.BeginFrameNeeded()) {
+    frame_source_->SetNeedsBeginFrames(true);
+  } else if (state_machine_.begin_impl_frame_state() ==
+             SchedulerStateMachine::BEGIN_IMPL_FRAME_STATE_IDLE) {
+    frame_source_->SetNeedsBeginFrames(false);
+    client_->SendBeginMainFrameNotExpectedSoon();
   }
-
-  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 354 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();
+
+  SetNeedsBeginFrameIfNeeded();
 }
 
 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 64 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