We probably need to just set this field as unknown when serializing SkMatrix.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/3af8e2d75b4b325f751ab8bc7624799b9f48835e

commit 3af8e2d75b4b325f751ab8bc7624799b9f48835e
Author: Adrienne Walker <enne@chromium.org>
Date: Thu Sep 14 22:53:56 2017

cc: Invalidate SkMatrix type after deserializing

This is not a safe field to serialize as malicious clients can lie about
what kind of matrix this is, which causes Skia asserts.  Fix this by
clearing this field after serializing.

Bug:  763668 
Cq-Include-Trybots: master.tryserver.blink:linux_trusty_blink_rel
Change-Id: I7f1ad8c7e1a556af6beed205406693b69bd2b622
Reviewed-on: https://chromium-review.googlesource.com/667796
Reviewed-by: Vladimir Levin <vmpstr@chromium.org>
Commit-Queue: enne <enne@chromium.org>
Cr-Commit-Position: refs/heads/master@{#502071}
[modify] https://crrev.com/3af8e2d75b4b325f751ab8bc7624799b9f48835e/cc/paint/paint_op_buffer.cc
[modify] https://crrev.com/3af8e2d75b4b325f751ab8bc7624799b9f48835e/cc/paint/paint_op_buffer_unittest.cc

ClusterFuzz has detected this issue as fixed in range 502042:502118.

Detailed report: https://clusterfuzz.com/testcase?key=5787848946221056

Fuzzer: libFuzzer_paint_op_buffer_fuzzer
Job Type: libfuzzer_chrome_asan_debug
Platform Id: linux

Crash Type: Abrt
Crash Address: 0x03e900000707
Crash State:
  sk_abort_no_print
  SkMatrix::setTypeMask
  SkMatrix::invertNonIdentity
  
Sanitizer: address (ASAN)

Regressed: https://clusterfuzz.com/revisions?job=libfuzzer_chrome_asan_debug&range=496919:496954
Fixed: https://clusterfuzz.com/revisions?job=libfuzzer_chrome_asan_debug&range=502042:502118

Reproducer Testcase: https://clusterfuzz.com/download?testcase_id=5787848946221056

See https://chromium.googlesource.com/chromium/src/+/master/testing/libfuzzer/reproducing.md for more information.

If you suspect that the result above is incorrect, try re-doing that job on the test case report page.

ClusterFuzz testcase 5787848946221056 is verified as fixed, so closing issue as verified.

If this is incorrect, please add ClusterFuzz-Wrong label and re-open the issue.