Always submit after texture uploads

Ensure GrContext::submit() is always called after either
Bitmap#prepareToDraw() or if DrawFrameTask skipped drawing.

In either case texture uploads & deletions will be scheduled,
but without the submit they won't actually be performed. This
can end up running out of RAM.

Bug: 189393671
Test: manual test app
Change-Id: I57477c64457558487e9e5ec0a979ad9099a8cb2c