Fix intermittent NPE in DrawerLayout.

- This required patching one of the components in the actual v4 Support
  library. We'll monitor the bug on Google (that I submitted), and see
  what solution they suggest:
  https://code.google.com/p/android/issues/detail?id=77926
- Also removed FixedFragmentStatePagerAdapter, since we're no longer using
  it.

Bug: 67808
Change-Id: Ia0b1246659c3f89e915350cc80792b545eece4f9