Replace replaceSurfaceDrawContext with replaceBackingProxy

Change-Id: Iba2641f71bdc541d1a55a22c022031949c326c27
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/414444
Commit-Queue: Robert Phillips <robertphillips@google.com>
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
7 files changed