Updates from API review.

    * AccessibilityService -- document onBind() to not be implemented.
    * GestureLibrary.getLearner() -- needs to be hidden.
    * IntentSender -- remove protected constructors, document that it is retrieved from a PendingIntent.
    * Hide permissions: SHUTDOWN, STOP_APP_SWITCHES.
    * Context -- hide BACKUP_SERVICE.
    * ContextWrapper -- hide getSharedPrefs bla h blah
    * Intent.parseUri() -- fix docs.
    * ApplicationInfo.FLAG_TEST_ONLY?!?
    * Hide MockContext.getSharedPrefs blah blah