Improve reliability work more mocking

Also, lots of experiment code copied from ADT source:

https://android.googlesource.com/platform/sdk/+/master/eclipse/plugins/com.android.ide.eclipse.adt/src/com/android/ide/eclipse/adt/internal/editors/common/

Can't seem to get ADT to return resource name suggestions, or really
any attribute value. I also can't seem to find the code where it
*would* provide that, either. It doesn't look like the
LayoutContentAssist even attempts to provide anything besides
layout/view names and their attributes, but I don't see anything
that would suggest that the ContentAssists are composed in any way
(and I don't see anything else providing resource suggestions
inside of attribute values, either... argh.) It's got to be there
somewhere.....