Revert of First set of WebUSB layout tests with Mojo service mocks. (patchset #3 id:40001 of https://codereview.chromium.org/1726943002/ )

Reason for revert:
Odd, I'm not sure what happened, but these layout tests appear to have passed the trybots and crashed on the waterfall bots:

https://build.chromium.org/p/chromium.webkit/builders/WebKit%20Win7/builds/39956
https://build.chromium.org/p/chromium.webkit/builders/WebKit%20Mac10.9/builds/28655

Original issue's description:
> First set of WebUSB layout tests with Mojo service mocks.
>
> This patch adds a minimal set of layout tests for the WebUSB API that
> work by registering mock implementations of the Mojo services the Blink
> implementation depends on. Since these mocks are implemented using the
> Javascript Mojo bindings they can live right next to the tests that
> depend on them.
>
> BUG=492204
>
> Committed: https://crrev.com/a6f677309a7741a1b9d6f6c510ee8282bfbff8c8
> Cr-Commit-Position: refs/heads/master@{#377429}

TBR=rockot@chromium.org,reillyg@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=492204

Review URL: https://codereview.chromium.org/1734753003

Cr-Commit-Position: refs/heads/master@{#377519}
6 files changed