Plugin Power Saver: Implement pixel tests for plugin placeholders.

chrome/test/base/ui_test_utils.h

Index: chrome/test/base/ui_test_utils.h
diff --git a/chrome/test/base/ui_test_utils.h b/chrome/test/base/ui_test_utils.h
index cd95c4b87f72934b66fd4638bcf93cedd12c7859..4ee85a5d9acb4a8dfbdd8fd476b3f52710c228ee 100644
--- a/chrome/test/base/ui_test_utils.h
+++ b/chrome/test/base/ui_test_utils.h
@@ -162,6 +162,9 @@ void GetCookies(const GURL& url,
                 int* value_size,
                 std::string* value);
 
+// Runs the current MessageLoop until |condition| is true or timeout.
+bool RunLoopUntil(const base::Callback<bool()>& condition);
+
 // A WindowedNotificationObserver hard-wired to observe
 // chrome::NOTIFICATION_TAB_ADDED.
 class WindowedTabAddedNotificationObserver