turn on alignment sanitizer

This sanitizer checks for overaligned reads and writes,
or put another way, use of underaligned pointers.

This usually happens when you cast, e.g. char* to int*
without checking that the char* is 4-byte aligned.  Each
of the changes under src/ fixes something just like that.

The unusual setup for tools/xsan.blacklist is there to
force a rebuild whenever tools/xsan.blacklist changes.
I spent a good few minutes debugging rebuilds not happening
this morning, perhaps from some strange ccache interaction.

Align SkTextBlobs as void* (today they're just 4-byte) so the
SkTextBlob::RunRecords we put after them in SkTextBlobBuilder
buffers are properly aligned (for the SkTypeface* inside).

There's no obvious error in void SkRRect::computeType(),
but one bot seems to have seen some sort of issue with

    SK_AT_SCOPE_EXIT(SkASSERT(this->isValid()));

I can't reproduce it locally, so I'm just going to unroll it.

Change-Id: I904d94f65f695e1b626b684c32216a4930b72b0c
Reviewed-on: https://skia-review.googlesource.com/146104
Commit-Queue: Mike Klein <mtklein@google.com>
Reviewed-by: Florin Malita <fmalita@chromium.org>
Reviewed-by: Mike Reed <reed@google.com>
Reviewed-by: Ben Wagner <bungeman@google.com>
7 files changed