Roll external/skia 7825d4983..f6da14697 (5 commits)

https://skia.googlesource.com/skia.git/+log/7825d4983..f6da14697

2019-07-11 bsalomon@google.com Move compatible stencil tracking from GrGLCaps::fConfigTable to ::fFormatTable.
2019-07-11 jvanverth@google.com New approach to fixing Vulkan MSAA.
2019-07-11 rmistry@google.com [perf_skottiewasm_lottieweb] Do 2 loops with 25 points each and then pick 25 from the middle
2019-07-11 jvanverth@google.com Remove deprecated discard method and GrCaps support
2019-07-11 mtklein@google.com instructions for JIT tail support on ARM

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Change-Id: Ic84dc7e8d6cc7645dc119ab93b0f6dcc50d3802d
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