Roll src/third_party/skia cd5d14619fe2..68eb8c276355 (4 commits) (#8815)

https://skia.googlesource.com/skia.git
/%2Blog/cd5d14619fe2..68eb8c276355

git log cd5d14619fe2673ccf903c785a984633cc555a44..68eb8c276355687ccd3f56f2279232f7fe1a9ebc --date=short --no-merges --format=%ad %ae %s
2019-05-02 reed@google.com remove deprecated postTranslate255
2019-05-01 robertphillips@google.com Change opList-splitting reduction default to be off
2019-05-02 halcanary@google.com SkPDF: fix repeat tilemode with alpha
2019-05-02 robertphillips@google.com Really disable opList splitting reduction on the Chorizo perf and test bots

The AutoRoll server is located here: https://autoroll.skia.org/r/skia-flutter-autoroll

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

If the roll is causing failures, please contact the current sheriff (ethannicholas@google.com), and stop
the roller if necessary.

DEPS

@@ -23,7 +23,7 @@ vars = {
   'fuchsia_git': 'https://fuchsia.googlesource.com',
   'github_git': 'https://github.com',
   'skia_git': 'https://skia.googlesource.com',
-  'skia_revision': 'cd5d14619fe2673ccf903c785a984633cc555a44',
+  'skia_revision': '68eb8c276355687ccd3f56f2279232f7fe1a9ebc',
 
   # 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

-Signature: 61ebfeb786df50543b0ae89ea1474e94
+Signature: f74704a33d8906cec9b1968b23b2f957
 
 UNUSED LICENSES:
 
@@ -5294,6 +5294,7 @@ FILE: ../../../third_party/skia/experimental/editor/editor_application.cpp
 FILE: ../../../third_party/skia/experimental/editor/run_handler.cpp
 FILE: ../../../third_party/skia/experimental/editor/run_handler.h
 FILE: ../../../third_party/skia/gm/crbug_918512.cpp
+FILE: ../../../third_party/skia/gm/tilemodes_alpha.cpp
 FILE: ../../../third_party/skia/src/gpu/GrPersistentCacheUtils.h
 FILE: ../../../third_party/skia/src/gpu/effects/GrComposeLerpEffect.fp
 FILE: ../../../third_party/skia/src/gpu/effects/GrComposeLerpRedEffect.fp