Fix a weird whitespace stripping bug

In HTML like <td>Foo <b>Bar</b></td>, the space would be stripped and
registered as trailing whitespace in the <td>, so it wouldn't be visible
in the editor and would be inserted after the </b> on the way out.

Thanks to Subbu for reporting this. This case was kind of ridiculous and
we're lucky the JRuby article contained it. To trigger the bug, you had
to have:
* a table cell
* containing unwrapped content
* consisting of
** some text
** whitespace
** open annotation (bold in my example, link in Subbu's case)
** text
** close annotation
** and nothing else

Change-Id: I2b83f02764b311a32a50956d4c8930a9394e91a4
Merge "Fix a weird whitespace stripping bug"