Start including 'winrt' in Windows toolchain

Recent versions of ANGLE require this. See:

  https://skia-review.googlesource.com/c/6698/

This also updates us to the latest version of the Windows SDK,
2015 Update 3 (Windows 10 SDK).

BUG=skia:
CQ_INCLUDE_TRYBOTS=skia.primary:Perf-Win2k8-MSVC-GCE-CPU-AVX2-x86_64-Debug-GDI,Test-Win10-MSVC-ShuttleA-GPU-GTX660-x86_64-Debug-Vulkan,Test-Win2k8-MSVC-GCE-CPU-AVX2-x86_64-Release

Change-Id: I42c8cabc87717f8695763f2c5573b27ab8ab65be
Reviewed-on: https://skia-review.googlesource.com/6801
Reviewed-by: Kevin Lubick <kjlubick@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
15 files changed