Remove unused Mac notification types

Their last listeners were removed in r593728 and their last broadcasters
were removed in r598355.

BUG=411569

Change-Id: I1471d4984a2e0439d29daf538972b317940af224
Reviewed-on: https://chromium-review.googlesource.com/c/1346835Reviewed-by: Devlin <rdevlin.cronin@chromium.org>
Commit-Queue: Avi Drissman <avi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#610154}

extensions/browser/notification_types.h

@@ -117,19 +117,6 @@ enum NotificationType {
   // (an extension ID and the name of the command being added).
   NOTIFICATION_EXTENSION_COMMAND_ADDED,
 
-  // Sent when an extension command shortcut for a browser action is activated
-  // on Mac. The source is the BrowserContext* and the details is a std::pair of
-  // a std::string containing an extension ID and a gfx::NativeWindow for the
-  // associated window.
-  NOTIFICATION_EXTENSION_COMMAND_BROWSER_ACTION_MAC,
-
-  // Sent when an extension command shortcut for a page action is activated
-  // on Mac. The source is the BrowserContext* and the details is a std::pair of
-  // a
-  // std::string containing an extension ID and a gfx::NativeWindow for the
-  // associated window.
-  NOTIFICATION_EXTENSION_COMMAND_PAGE_ACTION_MAC,
-
   // Sent by an extension to notify the browser about the results of a unit
   // test.
   NOTIFICATION_EXTENSION_TEST_PASSED,