Roll Skia from 8988cb464391 to 9c7e04cd6f37 (4 revisions)

https://skia.googlesource.com/skia.git/+log/8988cb464391..9c7e04cd6f37

2021-05-20 johnstiles@google.com Add support for do-while loops in PipelineStage.
2021-05-20 michaelludwig@google.com Support complex matrices in Image image filter
2021-05-19 johnstiles@google.com Eliminate unreachable code during optimization.
2021-05-19 skia-recreate-skps@skia-swarming-bots.iam.gserviceaccount.com Update SKP version

If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://autoroll.skia.org/r/skia-flutter-autoroll
Please CC bsalomon@google.com on the revert to ensure that a human
is aware of the problem.

To report a problem with the AutoRoller itself, please file a bug:
https://bugs.chromium.org/p/skia/issues/entry?template=Autoroller+Bug

Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+doc/master/autoroll/README.md

Author: skia-flutter-autoroll

DEPS

@@ -27,7 +27,7 @@ vars = {
   'skia_git': 'https://skia.googlesource.com',
   # OCMock is for testing only so there is no google clone
   'ocmock_git': 'https://github.com/erikdoe/ocmock.git',
-  'skia_revision': '8988cb46439179a8bf28fddf4891af3ea84bf73f',
+  'skia_revision': '9c7e04cd6f372c100e7a46d86a8841dff0d368fa',
 
   # When updating the Dart revision, ensure that all entries that are
   # dependencies of Dart are also updated to match the entries in the

ci/licenses_golden/licenses_skia

@@ -1,4 +1,4 @@
-Signature: 815402d675210fea37d2cc73ed46f986
+Signature: 348a81263eea5d1fd6c72b801e7a858a
 
 UNUSED LICENSES: