Browser Plugin: Disable context menu

Disable context menus inside guests until the Apps Context Menu API
is implemented for Browser Plugin.

BUG=140315


Review URL: https://chromiumcodereview.appspot.com/11030034

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@160289 0039d316-1c4b-4281-b951-d872f2087c98
2 files changed