This patch copies methods and classes from WireClient.cpp and
distributes them over multiple files. Headers and forward declarations
are added as necessary, but no logical changes are made.
Bug: dawn:88
Change-Id: I9d0fcaeb67e789c3ad0597eaa3839adefc3ac5f9
Reviewed-on: https://dawn-review.googlesource.com/c/3980
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Commit-Queue: Austin Eng <enga@chromium.org>