Add GPU memory usage contents browser test

chrome/browser/automation/testing_automation_provider.h

Index: chrome/browser/automation/testing_automation_provider.h
diff --git a/chrome/browser/automation/testing_automation_provider.h b/chrome/browser/automation/testing_automation_provider.h
index ca5340c69efff99a568088fb68e933da690fa0ce..60eb277eaa04cc8f7bf6dea737bfc43429b7578c 100644
--- a/chrome/browser/automation/testing_automation_provider.h
+++ b/chrome/browser/automation/testing_automation_provider.h
@@ -690,6 +690,11 @@ class TestingAutomationProvider : public AutomationProvider,
               base::DictionaryValue* args,
               IPC::Message* reply_message);
 
+  // Gets the current total global GPU memory usage.
+  void GetGpuMemoryUsage(Browser* browser,
+                         base::DictionaryValue* args,
+                         IPC::Message* reply_message);
+
   // Fullscreen and Mouse Lock hooks. They take no JSON parameters.
   void IsFullscreenForBrowser(Browser* browser,
             base::DictionaryValue* args,