Merges text nodes around comments.

Our text node handling currently assumes only one text node between
elements, and we ignore comments. Because of this, we need to merge
text nodes together in our representation.
redraw highlights after modifying in-browser DOM
Merge pull request #4705 from adobe/jasonsanjose/issue-4692

Redraw highlights after modifying in-browser DOM
Merge pull request #4703 from adobe/dangoor/merge-text

[Live HTML] Merge text nodes around comments
Merge branch 'ResearchLiveHTML' into dangoor/two-tags

Conflicts:
	test/spec/HTMLInstrumentation-test.js