Refactoring select popup on Mac....

Refactoring select popup on Mac.
The select popup on Mac was based on a hack: we would create an invisible RenderWidget and redirect mouse and keyboard events to it and we would display a native Cocoa menu. With this CL we do not use a RenderWidget anymore, we send the user selection to the RenderView which in turns communicates to WebKit that selection.

BUG=None
TEST=On Mac, ensures the select popup works as expected. Also test that for an extension with a browser action containing a select popup, the select popup does work. Also ensures autocomplete/autofill still works (especially popups).

Original review:
http://codereview.chromium.org/3795006/show


Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=63906