cc: Remove throttling of main frames for preventing NPAPI deadlock.

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 5d6f5895f34931adae9d37191f34e75f0e6fa6fd..ed2cb7a393370c22e4abe3cee2090561b7eafbbe 100644
--- a/cc/scheduler/scheduler_state_machine.cc
+++ b/cc/scheduler/scheduler_state_machine.cc
@@ -411,18 +411,6 @@ bool SchedulerStateMachine::CouldSendBeginMainFrame() const {
   return true;
 }
 
-bool SchedulerStateMachine::SendingBeginMainFrameMightCauseDeadlock() const {
-  // NPAPI is the only case where the UI thread makes synchronous calls to the
-  // Renderer main thread. During that synchronous call, we may not get a
-  // SwapAck for the UI thread, which may prevent BeginMainFrame's from
-  // completing if there's enough back pressure. If the BeginMainFrame can't
-  // make progress, the Renderer can't service the UI thread's synchronous call
-  // and we have deadlock.
-  // This returns true if there's too much backpressure to finish a commit
-  // if we were to initiate a BeginMainFrame.
-  return has_pending_tree_ && active_tree_needs_first_draw_ && SwapThrottled();
-}
-
 bool SchedulerStateMachine::ShouldSendBeginMainFrame() const {
   if (!CouldSendBeginMainFrame())
     return false;
@@ -459,9 +447,6 @@ bool SchedulerStateMachine::ShouldSendBeginMainFrame() const {
 
   // We need a new commit for the forced redraw. This honors the
   // single commit per interval because the result will be swapped to screen.
-  // TODO(brianderson): Remove this or move it below the
-  // SendingBeginMainFrameMightCauseDeadlock check since  we want to avoid
-  // ever returning true from this method if we might cause deadlock.
   if (forced_redraw_state_ == FORCED_REDRAW_STATE_WAITING_FOR_COMMIT)
     return true;
 
@@ -469,10 +454,6 @@ bool SchedulerStateMachine::ShouldSendBeginMainFrame() const {
   if (!HasInitializedOutputSurface())
     return false;
 
-  // Make sure the BeginMainFrame can finish eventually if we start it.
-  if (SendingBeginMainFrameMightCauseDeadlock())
-    return false;
-
   if (!settings_.main_frame_while_swap_throttled_enabled) {
     // SwapAck throttle the BeginMainFrames unless we just swapped to
     // potentially improve impl-thread latency over main-thread throughput.