Reland of cc: Remove frame queuing from the scheduler.

cc/scheduler/scheduler_state_machine.cc

Index: cc/scheduler/scheduler_state_machine.cc
diff --git a/cc/scheduler/scheduler_state_machine.cc b/cc/scheduler/scheduler_state_machine.cc
index 1f47e6145517b1c7449469d275036a05f056f67a..cc6cf17598b819161031dd53a15aa20a7095128a 100644
--- a/cc/scheduler/scheduler_state_machine.cc
+++ b/cc/scheduler/scheduler_state_machine.cc
@@ -365,6 +365,9 @@ bool SchedulerStateMachine::ShouldDraw() const {
   if (begin_impl_frame_state_ != BEGIN_IMPL_FRAME_STATE_INSIDE_DEADLINE)
     return false;
 
+  if (wait_for_ready_to_draw_)
+    return false;
+
   // Only handle forced redraws due to timeouts on the regular deadline.
   if (forced_redraw_state_ == FORCED_REDRAW_STATE_WAITING_FOR_DRAW)
     return true;
@@ -482,6 +485,10 @@ bool SchedulerStateMachine::ShouldCommit() const {
     return false;
   }
 
+  // Active tree resources might still be in use until the Display draws.
+  if (settings_.commit_to_active_tree && SwapThrottled())
+    return false;
+
   // If we only have an active tree, it is incorrect to replace it
   // before we've drawn it.
   DCHECK(!settings_.commit_to_active_tree || !active_tree_needs_first_draw_);
@@ -1025,11 +1032,6 @@ void SchedulerStateMachine::NotifyReadyToCommit() {
   DCHECK_EQ(begin_main_frame_state_, BEGIN_MAIN_FRAME_STATE_STARTED)
       << AsValue()->ToString();
   begin_main_frame_state_ = BEGIN_MAIN_FRAME_STATE_READY_TO_COMMIT;
-  // In commit_to_active_tree mode, commit should happen right after
-  // BeginFrame, meaning when this function is called, next action should be
-  // commit.
-  if (settings_.commit_to_active_tree)
-    DCHECK(ShouldCommit());
 }
 
 void SchedulerStateMachine::BeginMainFrameAborted(CommitEarlyOutReason reason) {