Roll src/third_party/skia 120e7d6766e4..50f377e275c3 (7 commits) (#12224)

https://skia.googlesource.com/skia.git/+log/120e7d6766e4..50f377e275c3

git log 120e7d6766e4..50f377e275c3 --date=short --no-merges --format='%ad %ae %s'
2019-09-11 kjlubick@google.com [canvaskit] expose ComputeTonalColors
2019-09-11 robertphillips@google.com Update comparison in BackendAllocation tests
2019-09-11 kjlubick@google.com [canvaskit] expose all 8 radii for RRect
2019-09-11 nigeltao@google.com Add a GifTest for the Haeberli hack
2019-09-11 recipe-mega-autoroller@chops-service-accounts.iam.gserviceaccount.com Roll recipe dependencies (trivial).
2019-09-11 benjaminwagner@google.com Omit benches that time out on Pixel3a
2019-09-11 benjaminwagner@google.com Update to XCode 10.3

Created with:
  gclient setdep -r src/third_party/skia@50f377e275c3

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 mtklein@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/+/master/autoroll/README.md

Bug: None
TBR=mtklein@google.com

DEPS

@@ -26,7 +26,7 @@ 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': '120e7d6766e4015528894e1c5c7f0d73bb091bf7',
+  'skia_revision': '50f377e275c34fc29fd142b62736b7bc553baa9b',
 
   # 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: c125b37166395d942a9bf69db5d6fd46
+Signature: ea72b0375f261e7962a6bdc7a923ae91
 
 UNUSED LICENSES:
 
@@ -1403,6 +1403,7 @@ FILE: ../../../third_party/skia/infra/bots/recipe_modules/build/examples/full.ex
 FILE: ../../../third_party/skia/infra/bots/recipe_modules/build/examples/full.expected/Build-Debian9-GCC-x86_64-Release-ANGLE.json
 FILE: ../../../third_party/skia/infra/bots/recipe_modules/build/examples/full.expected/Build-Debian9-GCC-x86_64-Release-NoGPU.json
 FILE: ../../../third_party/skia/infra/bots/recipe_modules/build/examples/full.expected/Build-Debian9-GCC-x86_64-Release-Shared.json
+FILE: ../../../third_party/skia/infra/bots/recipe_modules/build/examples/full.expected/Build-Mac-Clang-arm-Debug-iOS.json
 FILE: ../../../third_party/skia/infra/bots/recipe_modules/build/examples/full.expected/Build-Mac-Clang-arm64-Debug-Android_Vulkan.json
 FILE: ../../../third_party/skia/infra/bots/recipe_modules/build/examples/full.expected/Build-Mac-Clang-arm64-Debug-iOS.json
 FILE: ../../../third_party/skia/infra/bots/recipe_modules/build/examples/full.expected/Build-Mac-Clang-x86_64-Debug-ASAN.json
@@ -1497,6 +1498,7 @@ FILE: ../../../third_party/skia/infra/bots/recipes/perf.expected/Perf-Android-Cl
 FILE: ../../../third_party/skia/infra/bots/recipes/perf.expected/Perf-Android-Clang-Nexus5x-GPU-Adreno418-arm64-Release-All-Android_Vulkan.json
 FILE: ../../../third_party/skia/infra/bots/recipes/perf.expected/Perf-Android-Clang-Nexus7-CPU-Tegra3-arm-Debug-All-Android.json
 FILE: ../../../third_party/skia/infra/bots/recipes/perf.expected/Perf-Android-Clang-P30-GPU-MaliG76-arm64-Release-All-Android_Vulkan.json
+FILE: ../../../third_party/skia/infra/bots/recipes/perf.expected/Perf-Android-Clang-Pixel3a-GPU-Adreno615-arm64-Release-All-Android.json
 FILE: ../../../third_party/skia/infra/bots/recipes/perf.expected/Perf-ChromeOS-Clang-ASUSChromebookFlipC100-GPU-MaliT764-arm-Release-All.json
 FILE: ../../../third_party/skia/infra/bots/recipes/perf.expected/Perf-ChromeOS-Clang-AcerChromebook13_CB5_311-GPU-TegraK1-arm-Release-All.json
 FILE: ../../../third_party/skia/infra/bots/recipes/perf.expected/Perf-Chromecast-Clang-Chorizo-CPU-Cortex_A7-arm-Debug-All.json