Refactor memory interceptor test fixture into a class.

Refactor memory interceptor test fixture into a class.

R=sebmarchand@chromium.org

Committed: https://code.google.com/p/sawbuck/source/detail?r=2249

[Siggi, 2014-08-08 16:35:37]

Hey Sebastien,

in preparation for reusing or moving the ASAN memory accessor scaffolding, I've
refactored it into a class. I wanted this to be a minimal-ish change, so while
there's still moar work to do, that'd better be a separate CL.

Siggi

[Sébastien Marchand, 2014-08-08 17:03:16]

lgtm, thanks for cleaning this.

[Siggi, 2014-08-09 15:14:47]

Committed patchset #1 manually as 2249 (presubmit successful).