Make clearing by type actually work

Clearing by type in SurfaceFragment didn't actually work. Instead,
it followed a code path intended for setting and created an annotation
of that type with no data, then tried to clear that. What we really
want to do there is clear anything with that type.

This fixes the bug where unbolding of text that was already bold in
the article didn't work.

Bug: 47680
Change-Id: I77f00e63c8732420063b0453fede7f453083c913
Merge "Make clearing by type actually work"