Add API for nested pre-processing of a11y events; fix ResolverDrawerLayout

Add API for handling nested pre-processing of accessibility events
similar to nested pre-scroll or pre-fling. This allows custom views to
delegate a nested scroll to a parent via the accessibility system.

Use this functionality to allow opening the ResolverDrawerLayout via
accessibility commands.

Bug 18827274

Change-Id: Icd5a502605b78a861bb03e7b11923841a72eb9ab