cc: Add debug info for unexpected SwapBuffersComplete

Unexpected SwapBuffersComplete's can arrive for two common reasons:
1) DidSwapBuffersComplete is getting called before DidSwapBuffers.
2) A swap ack from the previous OutputSurface arrives.

This extra debug info will allow us to determine which case
we are in.

BUG=495650
CQ_INCLUDE_TRYBOTS=tryserver.blink:linux_blink_rel

Review URL: https://codereview.chromium.org/1153283009

Cr-Commit-Position: refs/heads/master@{#333148}

cc/scheduler/scheduler.cc

@@ -226,6 +226,7 @@ void Scheduler::DidSwapBuffers() {
 }
 
 void Scheduler::DidSwapBuffersComplete() {
+  DCHECK_GT(state_machine_.pending_swaps(), 0) << AsValue()->ToString();
   state_machine_.DidSwapBuffersComplete();
   ProcessScheduledActions();
 }
@@ -772,14 +773,16 @@ void Scheduler::AsValueInto(base::trace_event::TracedValue* state) const {
                    estimated_parent_draw_time_.InMillisecondsF());
   state->SetBoolean("last_set_needs_begin_frame_",
                     frame_source_->NeedsBeginFrames());
-  state->SetInteger("begin_retro_frame_args_",
+  state->SetInteger("begin_retro_frame_args",
                     static_cast<int>(begin_retro_frame_args_.size()));
-  state->SetBoolean("begin_retro_frame_task_",
+  state->SetBoolean("begin_retro_frame_task",
                     !begin_retro_frame_task_.IsCancelled());
-  state->SetBoolean("begin_impl_frame_deadline_task_",
+  state->SetBoolean("begin_impl_frame_deadline_task",
                     !begin_impl_frame_deadline_task_.IsCancelled());
-  state->SetBoolean("advance_commit_state_task_",
+  state->SetBoolean("advance_commit_state_task",
                     !advance_commit_state_task_.IsCancelled());
+  state->SetString("inside_action",
+                   SchedulerStateMachine::ActionToString(inside_action_));
   state->BeginDictionary("begin_impl_frame_args");
   begin_impl_frame_tracker_.AsValueInto(Now(), state);
   state->EndDictionary();

cc/scheduler/scheduler_state_machine.cc

@@ -34,6 +34,7 @@ SchedulerStateMachine::SchedulerStateMachine(const SchedulerSettings& settings)
       consecutive_checkerboard_animations_(0),
       max_pending_swaps_(1),
       pending_swaps_(0),
+      swaps_with_current_output_surface_(0),
       needs_redraw_(false),
       needs_animate_(false),
       needs_prepare_tiles_(false),
@@ -217,6 +218,8 @@ void SchedulerStateMachine::AsValueInto(
                     consecutive_checkerboard_animations_);
   state->SetInteger("max_pending_swaps_", max_pending_swaps_);
   state->SetInteger("pending_swaps_", pending_swaps_);
+  state->SetInteger("swaps_with_current_output_surface",
+                    swaps_with_current_output_surface_);
   state->SetBoolean("needs_redraw", needs_redraw_);
   state->SetBoolean("needs_animate_", needs_animate_);
   state->SetBoolean("needs_prepare_tiles", needs_prepare_tiles_);
@@ -1019,6 +1022,8 @@ void SchedulerStateMachine::SetMaxSwapsPending(int max) {
 
 void SchedulerStateMachine::DidSwapBuffers() {
   pending_swaps_++;
+  swaps_with_current_output_surface_++;
+
   DCHECK_LE(pending_swaps_, max_pending_swaps_);
 
   did_perform_swap_in_last_draw_ = true;
@@ -1026,7 +1031,6 @@ void SchedulerStateMachine::DidSwapBuffers() {
 }
 
 void SchedulerStateMachine::DidSwapBuffersComplete() {
-  DCHECK_GT(pending_swaps_, 0);
   pending_swaps_--;
 }
 
@@ -1144,6 +1148,7 @@ void SchedulerStateMachine::DidCreateAndInitializeOutputSurface() {
   }
   did_create_and_initialize_first_output_surface_ = true;
   pending_swaps_ = 0;
+  swaps_with_current_output_surface_ = 0;
 }
 
 void SchedulerStateMachine::NotifyBeginMainFrameStarted() {

cc/scheduler/scheduler_state_machine.h

@@ -179,6 +179,8 @@ class CC_EXPORT SchedulerStateMachine {
   // Notification from the OutputSurface that a swap has been consumed.
   void DidSwapBuffersComplete();
 
+  int pending_swaps() const { return pending_swaps_; }
+
   // Indicates whether to prioritize impl thread latency (i.e., animation
   // smoothness) over new content activation.
   void SetImplLatencyTakesPriority(bool impl_latency_takes_priority);
@@ -320,6 +322,7 @@ class CC_EXPORT SchedulerStateMachine {
   int consecutive_checkerboard_animations_;
   int max_pending_swaps_;
   int pending_swaps_;
+  int swaps_with_current_output_surface_;
   bool needs_redraw_;
   bool needs_animate_;
   bool needs_prepare_tiles_;