cc: Heuristic for Renderer latency recovery

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 2fbeca2d8a992d87cd118a09a78eeb5db8b61d3b..04bc61f666d1a4f03da2eb56923f3c1d677359b7 100644
--- a/cc/scheduler/scheduler_state_machine.cc
+++ b/cc/scheduler/scheduler_state_machine.cc
@@ -35,6 +35,8 @@ SchedulerStateMachine::SchedulerStateMachine(const SchedulerSettings& settings)
       consecutive_checkerboard_animations_(0),
       max_pending_swaps_(1),
       pending_swaps_(0),
+      swaps_are_likely_high_latency_(false),
+      swap_throttled_in_last_deadline_(false),
       needs_redraw_(false),
       needs_animate_(false),
       needs_prepare_tiles_(false),
@@ -818,6 +820,10 @@ bool SchedulerStateMachine::ProactiveBeginFrameWanted() const {
   return false;
 }
 
+void SchedulerStateMachine::DidSkipBeginImplFrameToReduceLatency() {
+  swaps_are_likely_high_latency_ = false;
+}
+
 void SchedulerStateMachine::OnBeginImplFrame() {
   begin_impl_frame_state_ = BEGIN_IMPL_FRAME_STATE_BEGIN_FRAME_STARTING;
   current_frame_number_++;
@@ -850,6 +856,10 @@ void SchedulerStateMachine::OnBeginImplFrameDeadline() {
 
   // Clear funnels for any actions we perform during the deadline.
   request_swap_funnel_ = false;
+
+  swap_throttled_in_last_deadline_ = pending_swaps_ >= max_pending_swaps_;
+  swaps_are_likely_high_latency_ =
+      swaps_are_likely_high_latency_ || swap_throttled_in_last_deadline_;
 }
 
 void SchedulerStateMachine::OnBeginImplFrameIdle() {
@@ -882,7 +892,6 @@ SchedulerStateMachine::CurrentBeginImplFrameDeadlineMode() const {
 
 bool SchedulerStateMachine::ShouldTriggerBeginImplFrameDeadlineImmediately()
     const {
-  // TODO(brianderson): This should take into account multiple commit sources.
   if (begin_impl_frame_state_ != BEGIN_IMPL_FRAME_STATE_INSIDE_BEGIN_FRAME)
     return false;
 
@@ -993,6 +1002,10 @@ void SchedulerStateMachine::DidSwapBuffers() {
 void SchedulerStateMachine::DidSwapBuffersComplete() {
   DCHECK_GT(pending_swaps_, 0);
   pending_swaps_--;
+
+  swaps_are_likely_high_latency_ =
+      begin_impl_frame_state_ == BEGIN_IMPL_FRAME_STATE_INSIDE_BEGIN_FRAME ||
+      swap_throttled_in_last_deadline_;
 }
 
 void SchedulerStateMachine::SetImplLatencyTakesPriority(