cc: Unify use of DidSwapBuffers() and did_request_swap

cc/scheduler/scheduler.cc

Index: cc/scheduler/scheduler.cc
diff --git a/cc/scheduler/scheduler.cc b/cc/scheduler/scheduler.cc
index 592cbf10dee350e459dd2e0ab24a32967b1d62f4..97098ec543fc316b27690f2a346a4f273e6e5ad3 100644
--- a/cc/scheduler/scheduler.cc
+++ b/cc/scheduler/scheduler.cc
@@ -98,6 +98,10 @@ void Scheduler::SetMaxSwapsPending(int 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_) {
@@ -450,8 +454,7 @@ void Scheduler::DrawAndSwapForced() {
 }
 
 void Scheduler::DrawAndReadback() {
-  DrawSwapReadbackResult result = client_->ScheduledActionDrawAndReadback();
-  DCHECK(!result.did_request_swap);
+  client_->ScheduledActionDrawAndReadback();
 }
 
 void Scheduler::ProcessScheduledActions() {