Do not do setSurface on window size changes

Surface should only be invalidated when surface generation changed
(which we're already doing). Window size change doesn't always imply
a surface change. During a drag-resizing action, the window size is
constantly changing but the surface remains the same. setSurface
could take 12ms+ each frame and cause frame drops.

bug: 23793966

Change-Id: Iac0456122e8916cf06b1a7a0940584ab4bf4065d