Roll external/skia b286bc2da..b5d8c634f (20 commits)

https://skia.googlesource.com/skia.git/+log/b286bc2da..b5d8c634f

2019-04-09 reed@google.com remove guard for bitmap shader api
2019-04-09 bsalomon@google.com Add support for importing GL_R16F for YUVA promise images
2019-04-09 martin@mainframe.co.uk add missing shared lib visibility macros
2019-04-09 herb@google.com Revert "Handle translating blob to origin in bulk"
2019-04-09 herb@google.com Revert "Reland "Do not use sub-pixel positioning for source space""
2019-04-09 skia-autoroll@skia-public.iam.gserviceaccount.com Roll skia/third_party/skcms 36eeb1311a72..0da672fc2c69 (1 commits)
2019-04-09 herb@google.com Reland "Add maxDimension() to glyph"
2019-04-09 herb@google.com Reland "Do not use sub-pixel positioning for source space"
2019-04-09 brianosman@google.com Shader serialization experiment (with Mali Offline Compiler analysis)
2019-04-09 reed@google.com Revert "Do not use sub-pixel positioning for source space"
2019-04-09 reed@google.com Revert "Add maxDimension() to glyph"
2019-04-09 robertphillips@google.com Revert "Skip flush in GrDrawingManager if the specifed proxy doesn't have any work"
2019-04-09 skia-recreate-skps@skia-swarming-bots.iam.gserviceaccount.com Update go_deps asset
2019-04-09 skia-autoroll@skia-public.iam.gserviceaccount.com Roll third_party/externals/swiftshader 4ba1911b2d7f..eba396cc66d3 (3 commits)
2019-04-09 skia-autoroll@skia-public.iam.gserviceaccount.com Roll third_party/externals/angle2 90b1865e2a8b..82418c821689 (8 commits)
2019-04-09 skia-autoroll@skia-public.iam.gserviceaccount.com Roll ../src afd96fdcf75a..79154509c679 (442 commits)
2019-04-09 recipe-mega-autoroller@chops-service-accounts.iam.gserviceaccount.com Roll recipe dependencies (trivial).
2019-04-08 fmalita@chromium.org [skottie] More snug kTop Shaper alignment
2019-04-08 gkaiser@google.com examples: Avoid undefined behavior
2019-04-08 reed@google.com undef guard for bitmap shader

The AutoRoll server is located here: https://autoroll-internal.skia.org/r/android-master-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, who should
be CC'd on the roll, and stop the roller if necessary.

Test: Presubmit checks will test this change.
Change-Id: I43e7a84291bd62216e314bf2e438210549b30ce3
Exempt-From-Owner-Approval: The autoroll bot does not require owner approval.