o Add user customizable launch type for apps by adding options in each apps context menu.
o Updated some comments that were using the outdated NOTIFY_PREF_CHANGED notification.
o Make LAUNCH_PINNED the default type returned by ExtensionPrefs if it does not already exist.
o Some minor refactoring within the code to reduce duplication.
BUG=54731
TEST=NONE
patch from issue
3419010
Review URL: http://codereview.chromium.org/
3453029
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@60997 0039d316-1c4b-4281-b951-d872f2087c98