Enabling audio quality test on mac.

Note: will land on Monday; need to watch bots so that they execute the
test right.

TBR=vrk@chromium.org
BUG=418034

Review URL: https://codereview.chromium.org/599103006

Cr-Commit-Position: refs/heads/master@{#297166}

chrome/browser/media/chrome_webrtc_audio_quality_browsertest.cc

@@ -378,10 +378,10 @@ bool RunPesq(const base::FilePath& reference_file,
   return true;
 }
 
-#if defined(OS_LINUX) || defined(OS_WIN)
-// Only implemented on Linux and Windows for now.
+#if defined(OS_LINUX) || defined(OS_WIN) || defined(OS_MACOSX)
 #define MAYBE_MANUAL_TestAudioQuality MANUAL_TestAudioQuality
 #else
+// Not implemented on Android, ChromeOS etc.
 #define MAYBE_MANUAL_TestAudioQuality DISABLED_MANUAL_TestAudioQuality
 #endif