ensure 4-byte alignment for storage, as SkWriterBuffer requires it

BUG=skia:3244

Review URL: https://codereview.chromium.org/805803002
Do circle anti-aliasing in normalized space to avoid precision issues with half-floats on Adreno.

Review URL: https://codereview.chromium.org/761593006
add dumpHex option to rect and rrect, to match path

BUG=skia:

Review URL: https://codereview.chromium.org/801383002