Add missing includes of SkBlendMode.h

It's being removed from SkPaint.h in https://skia-review.googlesource.com/c/skia/+/611077
and this was all the places I could find in frameworks/base.

We might need another CL for a few other Android repos.

Change-Id: I88d31166ed90356c4c52fbcde6bec6c1655b7cf2