The behavior is tested by NetworkContextConfigurationBrowserTest.Cache,
and the latter uses the correct URLRequestContext when the network
service is in use.

In another CL, I'll be switching the vestigal in-process system
URLRequestContext to use default parameters when the network service is
enabled, which will cause that context to use an in-memory cache. When
the network service is disabled, the legacy URLRequestContext will
still have no cache.  Seems best to just remove the test, since it's
redundant.

Bug: 754007
Change-Id: I0ce14ee613cf0d400d6fc86e8931eae370df13f5
Reviewed-on: https://chromium-review.googlesource.com/766951


Reviewed-by: Randy Smith <rdsmith@chromium.org>
Commit-Queue: Matt Menke <mmenke@chromium.org>
Cr-Commit-Position: refs/heads/master@{#516060}