PiP pinch-to-resize: add double-tap to max/min size.

Per spec, max size would be the biggest possible bounds within the
movement bounds (displayWidth - 2 * insetWidth), and min size would be
40% of the width.

This also fixes the issue of portrait PiP not resizing correctly due to
wrong math being done in the resize algorithm.

Bug: 166478885
Test: Double-tap on PiP
Change-Id: I2e239d23a0e2519c0b482005614a1faddb1f808a