cc: Unify use of DidSwapBuffers() and did_request_swap

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/logging.h"
@@ skipping 80 matching lines @@
   state_machine_.SetNeedsManageTiles();
   ProcessScheduledActions();
 }
 
 void Scheduler::SetMaxSwapsPending(int max) {
   state_machine_.SetMaxSwapsPending(max);
 }
 
 void Scheduler::DidSwapBuffers() {
   state_machine_.DidSwapBuffers();
+
+  // Swap should not occur by readback operation.
+  DCHECK(!IsInsideAction(SchedulerStateMachine::ACTION_DRAW_AND_READBACK));

[brianderson, 2014/04/24 01:54:15]

Can you move this DCHECK into the state machine? It should be easier to check
there.

[simonhong, 2014/04/25 01:13:37]

I tried but i think checking this condition in state machine is not easier than
here.
When state_machine::DidSwapBuffers() is called, all states were already
transited to next state.
Using IsInsideAction() in state machine can do but its not much difference.

+
   // There is no need to call ProcessScheduledActions here because
   // swapping should not trigger any new actions.
   if (!inside_process_scheduled_actions_) {
     DCHECK_EQ(state_machine_.NextAction(), SchedulerStateMachine::ACTION_NONE);
   }
 }
 
 void Scheduler::SetSwapUsedIncompleteTile(bool used_incomplete_tile) {
   state_machine_.SetSwapUsedIncompleteTile(used_incomplete_tile);
   ProcessScheduledActions();
@@ skipping 332 matching lines @@
   DrawSwapReadbackResult result =
       client_->ScheduledActionDrawAndSwapIfPossible();
   state_machine_.DidDrawIfPossibleCompleted(result.draw_result);
 }
 
 void Scheduler::DrawAndSwapForced() {
   client_->ScheduledActionDrawAndSwapForced();
 }
 
 void Scheduler::DrawAndReadback() {
-  DrawSwapReadbackResult result = client_->ScheduledActionDrawAndReadback();
-  DCHECK(!result.did_request_swap);
+  client_->ScheduledActionDrawAndReadback();
 }
 
 void Scheduler::ProcessScheduledActions() {
   // We do not allow ProcessScheduledActions to be recursive.
   // The top-level call will iteratively execute the next action for us anyway.
   if (inside_process_scheduled_actions_)
     return;
 
   base::AutoReset<bool> mark_inside(&inside_process_scheduled_actions_, true);
 
@@ skipping 109 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