Fix semantic HTML.

Applies recommendations by https://validator.w3.org/nu/:

 - Replaces untitled sections with divs.  (Sections are supposed to
   represent semantic, not structural, units.)
 - Replaces bookmark title h1. with h2s.  (While not strictly required
   according to the HTML spec, you are supposed to make heading levels
   independent of semantic structure tags.)

Change-Id: I81c634b67bb1044214b5f88a7e05f00d8ba87d5c
1 file changed