Roll src/third_party/skia fbc887d..25bc174 (7 commits) (#8039)

https://skia.googlesource.com/skia.git/%2Blog/fbc887df72ec..25bc174cf682

git log fbc887d..25bc174 --date=short --no-merges --format=%ad %ae %s
2019-03-04 skia-autoroll@skia-public.iam.gserviceaccount.com Roll third_party/externals/swiftshader bb30529..d318dd3 (7 commits)
2019-03-04 fmalita@chromium.org SkMixerColorFilter GPU impl
2019-03-04 csmartdalton@google.com Drop support for GL_EXT_raster_multisample
2019-03-05 skia-recreate-skps@skia-swarming-bots.iam.gserviceaccount.com Update go_deps asset
2019-03-01 bungeman@google.com Roll HarfBuzz.
2019-03-05 skia-autoroll@skia-public.iam.gserviceaccount.com Roll third_party/externals/angle2 0e1ce2e..b8cff9e (6 commits)
2019-03-05 recipe-roller@chromium.org Roll recipe dependencies (trivial).

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 (reed@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': 'fbc887df72ec102843c009977b24ed5b4bb2fab1',
+  'skia_revision': '25bc174cf682e666d5437e5f3b910a7a11b4bb9e',
 
   # 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: 8ba8b757d4d23dc9e9b1a157dc7ca2e2
+Signature: c8fbe627d3b7f9e585d53f4e8584f18b
 
 UNUSED LICENSES:
 
@@ -4862,6 +4862,9 @@ FILE: ../../../third_party/skia/src/gpu/GrImageContext.cpp
 FILE: ../../../third_party/skia/src/gpu/GrImageContextPriv.h
 FILE: ../../../third_party/skia/src/gpu/GrRecordingContext.cpp
 FILE: ../../../third_party/skia/src/gpu/GrRecordingContextPriv.h
+FILE: ../../../third_party/skia/src/gpu/effects/GrMixerEffect.cpp
+FILE: ../../../third_party/skia/src/gpu/effects/GrMixerEffect.fp
+FILE: ../../../third_party/skia/src/gpu/effects/GrMixerEffect.h
 FILE: ../../../third_party/skia/src/gpu/vk/GrVkSecondaryCBDrawContext.cpp
 FILE: ../../../third_party/skia/src/gpu/vk/GrVkSecondaryCBDrawContext.h
 FILE: ../../../third_party/skia/src/sksl/SkSLDefines.h