Verify if GPU message pump is signaled when it hangs in WaitForWork

base/message_loop/message_pump_win.h

Index: base/message_loop/message_pump_win.h
diff --git a/base/message_loop/message_pump_win.h b/base/message_loop/message_pump_win.h
index bf4cdaa8420b8ba3c6f2b9c81f5679a490c71138..84ee3cb561875f022109d3ee2c02e709e1e039ad 100644
--- a/base/message_loop/message_pump_win.h
+++ b/base/message_loop/message_pump_win.h
@@ -164,6 +164,13 @@ class BASE_EXPORT MessagePumpForGpu : public MessagePumpWin {
   void ScheduleWork() override;
   void ScheduleDelayedWork(const TimeTicks& delayed_work_time) override;
 
+  // TODO (stanisc): crbug.com/596190: Remove this after the signaling issue
+  // has been investigated.
+  // This should be used for diagnostic only. If message pump wake-up mechanism
+  // is based on auto-reset event this call would reset the event to unset
+  // state.
+  bool WasSignaled() override;
+
  private:
   // MessagePumpWin methods:
   void DoRunLoop() override;