Fix bug in disabling sync for default apps

We added a new creation_flag for default apps was_installed_by_default,
 but every time we add a new creation_flag, we need to update the installedLoader
 as it does not directly pick the creation_flags but re-creates them
 through other preferences.
To fix this, I added a new preference to save creation_flags in preference,
 and read that directly.

BUG=152582
TBR=nick@chromium.org

Review URL: https://chromiumcodereview.appspot.com/10977048

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@160259 0039d316-1c4b-4281-b951-d872f2087c98
17 files changed