[webcrypto] Add AES-GCM using NSS.

This requires NSS version 3.15 or greater. Since Linux Chrome is using the system NSS it may not work for Linux users unless they have a more recent NSS version. Mac and Windows builds however are not affected by this and it should just work.

BUG=245025

Review URL: https://codereview.chromium.org/115653002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@244845 0039d316-1c4b-4281-b951-d872f2087c98
Sync removal of Default apps.

This CL implements TYPE_REMOVE_DEFAULT_APP. It also includes a fair bit
of cleanup of AppListSyncableService, which on the one hand I apologize
for, but on the other hand I think the result is more straightforward.

BUG=258758

Review URL: https://codereview.chromium.org/118463002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@244846 0039d316-1c4b-4281-b951-d872f2087c98
Remove TODO about making WrenchMenuObserver an inner class of WrenchMenu.

Chromium code style says:
"Prefer putting delegate classes in their own header files. Implementors
of the
delegate interface will often be included elsewhere, which will often
cause more
coupling with the header of the main class."

http://www.chromium.org/developers/coding-style - Code formatting
section

BUG=None
R=sky@chromium.org
NOTRY=true

Review URL: https://codereview.chromium.org/118623003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@244848 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 244848