Add framework flag to allow enable/disable resize.

Some OEMs may not want the PIP window to resize on touch; this is true
for those that ship only large-screen form factor devices, so the PIP
window is already big enough for the controls (e.g. ChromeOS).

Bug: 148083488
Test: Build, touch - PIP does not resize.
Change-Id: I997c3f428981aafda4b6cffece355ba0cfdac4e6