Cherry-pick of https://skia.googlesource.com/skia.git/+/96c118edff293af93db0a2b1b6775428117924b1 to m39 branch

Change GrContext::copyTexture to go through GrDrawTarget

BUG=crbug.com/415100
R=bsalomon@google.com, robertphillips@google.com

Author: junov@chromium.org

Review URL: https://codereview.chromium.org/607993002

Conflicts:
	src/gpu/GrContext.cpp

Review URL: https://codereview.chromium.org/608353002
2 files changed