Remove forced commit and readback from the scheduler.

cc/scheduler/scheduler.cc

Index: cc/scheduler/scheduler.cc
diff --git a/cc/scheduler/scheduler.cc b/cc/scheduler/scheduler.cc
index f73efecf1177e953b6287d99a5b66cdf59149f05..e924d33884bf6dec6a758b4d640b8fef0fee8059 100644
--- a/cc/scheduler/scheduler.cc
+++ b/cc/scheduler/scheduler.cc
@@ -164,11 +164,6 @@ void Scheduler::SetNeedsCommit() {
   ProcessScheduledActions();
 }
 
-void Scheduler::SetNeedsForcedCommitForReadback() {
-  state_machine_.SetNeedsForcedCommitForReadback();
-  ProcessScheduledActions();
-}
-
 void Scheduler::SetNeedsRedraw() {
   state_machine_.SetNeedsRedraw();
   ProcessScheduledActions();
@@ -192,9 +187,6 @@ void Scheduler::SetMaxSwapsPending(int max) {
 void Scheduler::DidSwapBuffers() {
   state_machine_.DidSwapBuffers();
 
-  // Swap should not occur inside readback operation.
-  DCHECK(!IsInsideAction(SchedulerStateMachine::ACTION_DRAW_AND_READBACK));
-
   // There is no need to call ProcessScheduledActions here because
   // swapping should not trigger any new actions.
   if (!inside_process_scheduled_actions_) {
@@ -618,7 +610,6 @@ void Scheduler::ProcessScheduledActions() {
 
   SchedulerStateMachine::Action action;
   do {
-    state_machine_.CheckInvariants();
     action = state_machine_.NextAction();
     TRACE_EVENT1(TRACE_DISABLED_BY_DEFAULT("cc.debug.scheduler"),
                  "SchedulerStateMachine",
@@ -655,9 +646,6 @@ void Scheduler::ProcessScheduledActions() {
         // No action is actually performed, but this allows the state machine to
         // advance out of its waiting to draw state without actually drawing.
         break;
-      case SchedulerStateMachine::ACTION_DRAW_AND_READBACK:
-        client_->ScheduledActionDrawAndReadback();
-        break;
       case SchedulerStateMachine::ACTION_BEGIN_OUTPUT_SURFACE_CREATION:
         client_->ScheduledActionBeginOutputSurfaceCreation();
         break;