Always disable the scissor test before BlitFrameBuffer

It seems most (all?) implementations of BlitFrameBuffer actually
obey the scissor test, so just always disable the scissor before
calling BlitFrameBuffer.

Original Author: Henry Song <henrysong@samsung.com>

R=bsalomon@google.com, hcm@google.com

Author: derekf@osg.samsung.com

Review URL: https://codereview.chromium.org/574543002
2 files changed