subject in actionbar

Mostly a port of Gmail1 code. New and noteworthy:
* when switching between ActionBar list nav vs. custom display,
  toggle ActionBar.DISPLAY_SHOW_CUSTOM rather than messing with
  custom view visibility
  * This exposes something of a framework bug where collapsing
    an action view will leave views for all inactive navigation
    modes GONE, which I work around for now (b/6664203).
* ActionBar views were being inflated with system default Holo
  theme due to application vs. ActionBar context (wrong theme on
  the application context). Fixed that and un-inverted some
  existing styles.
* SnippetTextView: save off the last measurespec rather than
  inventing one as before.
* bring back an existing excellent behavior: since
  PagerAdapter.setPrimaryItem reacts too slowly to nicely
  change the action bar subject when paging, listen for
  OnPageChangeListener.onPageSelected in addition.

Bug: 6384157
Change-Id: I45d995a472d4b3c71f1371dc7b993923423b7cf7
20 files changed