Popup: blue focus flash on android 4.2

So I tested this with Browserstack on android 4.2 and it fixed the problem.  However, when I run "grunt test" there are a number of test cases failing.  @arschmitz suggested I do a pull request so he can take a look.  So don't merge if it's breaking tests! :)
We need to wrap the handler in ```$.proxy```, because the context inside the handler is not the widget instance but the element being focused. That is, we need to
```JS
				$( this.document[ 0 ].activeElement ).one( "focus",
					$.proxy( function(/* theEvent */) {
						this._safelyBlur( target[ 0 ] );
					}, this ) );
```