SkScalerContext to use smart pointers.

CQ_INCLUDE_TRYBOTS=master.client.skia:Test-Ubuntu-Clang-GCE-CPU-AVX2-x86_64-Debug-ASAN-Trybot;master.client.skia:Test-Ubuntu-Clang-GCE-CPU-AVX2-x86_64-Debug-MSAN-Trybot

Change-Id: I27a714388b8ded7dfc968e322b0a587205f575f1
Reviewed-on: https://skia-review.googlesource.com/3731
Reviewed-by: Mike Klein <mtklein@chromium.org>
Commit-Queue: Ben Wagner <bungeman@google.com>
19 files changed