Re-enable ExtensionApiTest.Messaging. It was disabled due to flakiness

over a year ago, but it's our only test for some features of extension
messaging, and we've recently been changing that.

If ExtensionApiTest.Messaging starts failing, this will be why. However,
don't get it confused with PlatformAppApiTest.Messaging. Those failures
are unrelated.

BUG=96725

Review URL: https://codereview.chromium.org/11778010

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@175458 0039d316-1c4b-4281-b951-d872f2087c98

chrome/browser/extensions/extension_messages_apitest.cc

@@ -77,8 +77,7 @@ class MessageSender : public content::NotificationObserver {
 }  // namespace
 
 // Tests that message passing between extensions and content scripts works.
-// Flaky on the trybots. See http://crbug.com/96725.
-IN_PROC_BROWSER_TEST_F(ExtensionApiTest, DISABLED_Messaging) {
+IN_PROC_BROWSER_TEST_F(ExtensionApiTest, Messaging) {
   ASSERT_TRUE(StartTestServer());
   ASSERT_TRUE(RunExtensionTest("messaging/connect")) << message_;
 }