Fix context menu handling for Bookmarks and History

 Bugs: 3125172 and 3102808
 BrowserActivity was trying (and failing) to handle context menu
 actions that came from fragments such as bookmarks and history.
 This fixes it so that BrowserActivity no longer tries to handle
 menus that it didn't create.

Change-Id: I09b5f36a0030f02de6ce09ac7588cb8c78394d39
2 files changed