Roll external/skia 4f94ef6cb..34e5e1b38 (5 commits)

https://skia.googlesource.com/skia.git/+log/4f94ef6cb..34e5e1b38

2018-09-12 mtklein@google.com switch Skia to explicit big-endian 16-bit skcms type
2018-09-12 halcanary@google.com SkPDF: SkPDFMakeArray; clean up pdfutils, pdfresourcedict
2018-09-12 angle-skia-autoroll@skia-buildbots.google.com.iam.gserviceaccount.com Roll third_party/externals/angle2 8370e6bcb369..85d8ee8c1fbf (2 commits)
2018-09-12 skcms-skia-autoroll@skia-buildbots.google.com.iam.gserviceaccount.com Roll skia/third_party/skcms 710aa46f904e..b9dc92669da2 (1 commits)
2018-09-12 skcms-skia-autoroll@skia-buildbots.google.com.iam.gserviceaccount.com Roll skia/third_party/skcms 52df767ea52b..710aa46f904e (1 commits)

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: Ibc19372bd8c3f870dce98a2ac06b50d93bd3e3a4
Exempt-From-Owner-Approval: The autoroll bot does not require owner approval.