Attempt to claim the drag event for the RangeBar

Without this, a parent that handles a swipe gesture (such as ViewPager
or ListView, etc) may intercept this child's touch events, and handle
them as its own gesture.  This method comes directly from the
inspiration of this widget:
https://github.com/android/platform_frameworks_base/blob/master/core/java/android/widget/AbsSeekBar.java#L454
Fix a Y-offset drawing issue from 0d81f260

The yPos might not be perfectly centered, based on the radius and
bar/line widths.

The correct Y-translation should be `mY - mHalfHeightNormal`