Roll external/skia 33cb22cb2..0c51eeada (31 commits)

https://skia.googlesource.com/skia.git/+log/33cb22cb2..0c51eeada

2018-03-09 bsalomon@google.com Add GrMockRenderTarget and mock backend render targets
2018-03-09 herb@google.com Remove last use of DetachCache.
2018-03-09 liyuqian@google.com Revert "Check the boundary while cumulating deltas in a mask"
2018-03-09 halcanary@google.com SkPDF: filter out empty clip draws more often
2018-03-09 jvanverth@google.com Add a negative translation to one of the smallpath GMs
2018-03-09 halcanary@google.com SkPDF: simplify PathOp code, emit empty clips.
2018-03-09 caryclark@skia.org add starting template support
2018-03-09 caryclark@google.com Revert "start hardening pathmeasure"
2018-03-09 liyuqian@google.com Check the boundary while cumulating deltas in a mask
2018-03-09 caryclark@skia.org start hardening pathmeasure
2018-03-09 bungeman@google.com IWYU for test files starting with 'B'.
2018-03-09 mtklein@chromium.org roll clang_linux package to Clang 6
2018-03-09 reed@google.com harden line clipper against slight numerical drift.
2018-03-09 herb@google.com Remove use of attach/detatch cache from distance field text
2018-03-09 jvanverth@google.com Fix issue with negative translations of small paths
2018-03-09 liyuqian@google.com Do not set record to empty if it's already computed
2018-03-09 reed@google.com Ensure Y->X ordering when building a region from a path
2018-03-09 brianosman@google.com Shim to enforce that canvas virtuals are overridden
2018-03-09 bungeman@google.com SkResourceCache.h shouldn't include itself.
2018-03-09 herb@google.com Remove TLS glyph cache calls.
2018-03-09 bsalomon@google.com Add GPUSink getters to suppress unused field warnings in no gpu build.
2018-03-09 herb@google.com Remove another set of AttachCache
2018-03-09 csmartdalton@google.com ccpr: Simplify triangle corners
2018-03-09 reed@google.com update tool to sniff images during deserialization
2018-03-09 egdaniel@google.com Fix no gpu build
2018-03-09 herb@google.com Remove getCache from SkAutoGlyphCache*
2018-03-09 bsalomon@google.com Fix breakage from merge conflict related to deleteTestingOnlyBackendTexture sig. change
2018-03-09 robertphillips@google.com Enable opList-based DDLs
2018-03-09 bsalomon@google.com Make GrGpu::deleteTestingOnlyBackendTexture() take const GrBackendTexture&
2018-03-09 brianosman@google.com Fix a logical test in GrColorSpaceXform::Equals
2018-03-09 egdaniel@google.com Add promise images for deferred instantiation of wrapped gpu textures

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Change-Id: I982e4faf47317d77c12e805542689961b421c346
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