Framework: Add Quick Message Support (2/2)

This commit makes the two EditText background drawables (holo_light
and holo_dark) publickly available as a resource.  This enabled the
overriding of the EditText background in user code.

Patch Set 2: Added missing @hide statements
Patch Set 3: Removed the @hide statements added by anoter gerrit
             user as they are not used in public.xml

Change-Id: Iff80e4ece16f873e45a84e92c88ebfab752afa1f