Remove using of setResizing in split screen

We use setResizing to draw app bottom background for reducing flicker
while split decor screen fade-in. But this cause another flicker after
resizing finished. Use split decor to draw a fill up background to
reduce flicker mentioned at first and remove using of setResizing.

Do some temp rect optimization in this CL too.

Fix: 235451160
Fix: 237040271
Fix: 238045271
Test: manual
Test: pass existing tests
Change-Id: I6b70f35d47ced78eaacc9ecd9ae1ebf3a11dbc1f