Fix flicker from multiwindow resize

Move content bounds into DrawFrameTask. This ensures
that changes in bounds are synchronized with changes in
rendering commands, avoiding potential underdraw.

Bug: 64200212
Test: Repro steps in bug. Drag up/down on resize handle, verify
no flicker.

Change-Id: I3109acf262e23c2a7d8904f1dcbfc8273aaed65b