Fix a threading bug in the brlapi basec braille controller

BUG=178559

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=225008

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=225398

Review URL: https://codereview.chromium.org/24325002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@226051 0039d316-1c4b-4281-b951-d872f2087c98
Remove shortcuts to extension URLs when the corresponding extensions are unloaded.

This also cleans up some style issues in the shortcuts backend, e.g. declaration order not matching definition order, and some sloppiness in the shortcuts provider.

BUG=151044
TEST=Install extension in bug comment 0, type "echo echo" in omnibox, hit enter, uninstall extension, type "echo", the dropdown should not have a shortcut to the extension.
R=bartn@chromium.org, brettw@chromium.org

Review URL: https://codereview.chromium.org/25042005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@226053 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 226051
SVN changes up to revision 226053