Pack and align SkStrokeRec to 4-byte boundary.

The new key for the distance field path cache will contain an
SkStrokeRec. This change guarantees that we don't have any hidden
padding that has garbage values, thereby preventing apparently
equal keys from hashing to two different values. This also has
the nice effect of reducing the size of SkStrokeRec from 24 bytes
to 16 bytes.

Review URL: https://codereview.chromium.org/1465773003
2 files changed