Re-enabling 720p webcam test for QTKit on Mac.

mcasas tested it and it appears to work now.

BUG=440762

Review URL: https://codereview.chromium.org/1039163002

Cr-Commit-Position: refs/heads/master@{#322572}

chrome/browser/media/chrome_webrtc_webcam_browsertest.cc

@@ -97,13 +97,13 @@ IN_PROC_BROWSER_TEST_P(WebRtcWebcamBrowserTest,
             GetUserMediaAndGetStreamSize(tab, kVideoCallConstraintsVGA));
   EXPECT_EQ("640x360",
             GetUserMediaAndGetStreamSize(tab, kVideoCallConstraints360p));
+  EXPECT_EQ("1280x720",
+            GetUserMediaAndGetStreamSize(tab, kVideoCallConstraints720p));
 
-  // QTKit supports up to 480p (used to support 720p until crbug.com/440762).
+  // QTKit only supports up to 720p.
   if (IsOnQtKit())
     return;
 
-  EXPECT_EQ("1280x720",
-            GetUserMediaAndGetStreamSize(tab, kVideoCallConstraints720p));
   EXPECT_EQ("1920x1080",
             GetUserMediaAndGetStreamSize(tab, kVideoCallConstraints1080p));
 }