Disallow burst context instantiation for non-invertible CTMs

Similar to SkShaderBase::makeContext(), catch this condition and bail
early.

BUG=chromium:738682

Change-Id: I4c7a2036bed8ab8699023c4f8f3bc2161de0c41d
Reviewed-on: https://skia-review.googlesource.com/21521
Reviewed-by: Herb Derby <herb@google.com>
Commit-Queue: Florin Malita <fmalita@chromium.org>
1 file changed