Roll external/skia 9661b9822..d23d8d1d9 (2 commits)

https://skia.googlesource.com/skia.git/+log/9661b9822..d23d8d1d9

2018-01-07 reed@google.com remove guarded old malloc code
2018-01-07 fmalita@chromium.org [skotty,sksg] Initial trim path effect

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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
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Test: Presubmit checks will test this change.
Change-Id: Ifc3994064f8dd4210cd1092c5bea126a99bf99c5
Exempt-From-Owner-Approval: The autoroll bot does not require owner approval.