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

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 2bec4de837494ae42052cd839f0001e880428d44..528fe8e838ded4eab880154b66b4f1366707797e 100644
--- a/cc/scheduler/scheduler_state_machine.cc
+++ b/cc/scheduler/scheduler_state_machine.cc
@@ -1086,4 +1086,17 @@ bool SchedulerStateMachine::HasInitializedOutputSurface() const {
   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