Avoid double-destruction of Sk3DShaderContext-wrapped objects

Sk3DShaderContext creates its nested shader context on a SkArenaAlloc,
which handles destruction when going out of scope.

Hence, the explicit context dtor call in ~Sk3DShaderContext() is
incorrect (likely left over from before SkArenaAlloc).

BUG=chromium:787712

Change-Id: I176222e449151dcce532a839ef9587d06f61d297
Reviewed-on: https://skia-review.googlesource.com/77203
Commit-Queue: Herb Derby <herb@google.com>
Reviewed-by: Herb Derby <herb@google.com>
2 files changed