Add more logging to cc scheduler to debug RAF frame loss.

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 1068 matching lines @@
 
     case OUTPUT_SURFACE_ACTIVE:
     case OUTPUT_SURFACE_WAITING_FOR_FIRST_COMMIT:
     case OUTPUT_SURFACE_WAITING_FOR_FIRST_ACTIVATION:
       return true;
   }
   NOTREACHED();
   return false;
 }
 
+std::string SchedulerStateMachine::GetStatesForDebugging() const {
+  return base::StringPrintf("%c %d %d %d %c %c %c %d %d",
+      needs_commit_ ? 'T' : 'F',
+      static_cast<int>(output_surface_state_),
+      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