Attempt to fix flaky ChromeOS test timeouts.

cc/scheduler/scheduler_state_machine.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_state_machine.h"
 
 #include "base/debug/trace_event.h"
 #include "base/debug/trace_event_argument.h"
 #include "base/format_macros.h"
 #include "base/logging.h"
@@ skipping 302 matching lines @@
   // We only want to start output surface initialization after the
   // previous commit is complete.
   if (commit_state_ != COMMIT_STATE_IDLE)
     return false;
 
   // Make sure the BeginImplFrame from any previous OutputSurfaces
   // are complete before creating the new OutputSurface.
   if (begin_impl_frame_state_ != BEGIN_IMPL_FRAME_STATE_IDLE)
     return false;
 
-  // We want to clear the pipeline of any pending draws and activations
+  // We want to clear the pipline of any pending draws and activations
   // before starting output surface initialization. This allows us to avoid
   // weird corner cases where we abort draws or force activation while we
   // are initializing the output surface.
   if (active_tree_needs_first_draw_ || has_pending_tree_)
     return false;
 
   // We need to create the output surface if we don't have one and we haven't
   // started creating one yet.
   return output_surface_state_ == OUTPUT_SURFACE_LOST;
 }
 
 bool SchedulerStateMachine::ShouldDraw() const {
   // If we need to abort draws, we should do so ASAP since the draw could
   // be blocking other important actions (like output surface initialization),
-  // from occurring. If we are waiting for the first draw, then perform the
+  // from occuring. If we are waiting for the first draw, then perfom the
   // aborted draw to keep things moving. If we are not waiting for the first
   // draw however, we don't want to abort for no reason.
   if (PendingDrawsShouldBeAborted())
     return active_tree_needs_first_draw_;
 
   // After this line, we only want to send a swap request once per frame.
   if (HasRequestedSwapThisFrame())
     return false;
 
   // Do not queue too many swaps.
@@ skipping 118 matching lines @@
     return true;
 
   // After this point, we only start a commit once per frame.
   if (HasSentBeginMainFrameThisFrame())
     return false;
 
   // We shouldn't normally accept commits if there isn't an OutputSurface.
   if (!HasInitializedOutputSurface())
     return false;
 
+  // SwapAck throttle the BeginMainFrames unless we just swapped.
+  // TODO(brianderson): Remove this restriction to improve throughput.
+  bool just_swapped_in_deadline =
+      begin_impl_frame_state_ == BEGIN_IMPL_FRAME_STATE_INSIDE_DEADLINE &&
+      HasSwappedThisFrame();
+  if (pending_swaps_ >= max_pending_swaps_ && !just_swapped_in_deadline)
+    return false;
+
   if (skip_begin_main_frame_to_reduce_latency_)
     return false;
 
   return true;
 }
 
 bool SchedulerStateMachine::ShouldCommit() const {
   if (commit_state_ != COMMIT_STATE_READY_TO_COMMIT)
     return false;
 
@@ skipping 596 matching lines @@
       static_cast<int>(begin_impl_frame_state_),
       static_cast<int>(commit_state_),
       has_pending_tree_ ? 'T' : 'F',
       pending_tree_is_ready_for_activation_ ? 'T' : 'F',
       active_tree_needs_first_draw_ ? 'T' : 'F',
       max_pending_swaps_,
       pending_swaps_);
 }
 
 }  // namespace cc