cc: DCHECK if SDOS::SwapBuffersComplete is called prematurely

cc/scheduler/scheduler.cc

Index: cc/scheduler/scheduler.cc
diff --git a/cc/scheduler/scheduler.cc b/cc/scheduler/scheduler.cc
index 0d90c68214f15a822f66419d899885b7a4e84e56..2d64e56eb7aabbf9f6f4e86dd1cca4590ec5e75e 100644
--- a/cc/scheduler/scheduler.cc
+++ b/cc/scheduler/scheduler.cc
@@ -7,6 +7,7 @@
 #include <algorithm>
 
 #include "base/auto_reset.h"
+#include "base/debug/stack_trace.h"
 #include "base/logging.h"
 #include "base/profiler/scoped_tracker.h"
 #include "base/single_thread_task_runner.h"
@@ -226,7 +227,8 @@ void Scheduler::DidSwapBuffers() {
 }
 
 void Scheduler::DidSwapBuffersComplete() {
-  DCHECK_GT(state_machine_.pending_swaps(), 0) << AsValue()->ToString();
+  DCHECK_GT(state_machine_.pending_swaps(), 0)
+      << AsValue()->ToString() << base::debug::StackTrace().ToString();
   state_machine_.DidSwapBuffersComplete();
   ProcessScheduledActions();
 }