Fix for TitlePageIndicator incomplete animation ("stuck" between tabs).

There are actually two issues:

ViewPager doesn't always emit every onPageScrolled event, so
onPageScrollStateChanged(SCROLL_STATE_IDLE) can be called while
mPageOffset is still > 0. This issue seems to happen when the UI drops
frames.

onPageSelected can be called while scrolling is not idle causing
mCurrentPage to not be updated before
onPageScrollStateChanged(SCROLL_STATE_IDLE). This happens when calling
viewPager.setCurrentItem directly, such as by tapping on another tab.