Store network_service cache in memory

Store network_service cache in memory

The network cache is not safe for usage by multiple processes at the same
time like when sky tests are running many mojo_shell instances in parallel.
To work around this we store the cache in memory. In the future we should
consider file system partitioning for mojo services.

R=davemoore@chromium.org

Committed: https://chromium.googlesource.com/external/mojo/+/d2c4163b85c39217c191c48f4732723681209f4a

[esprehn, 2014-10-28 18:18:06]

esprehn@chromium.org changed reviewers:
+ davemoore@chromium.org, ojan@chromium.org

[DaveMoore, 2014-10-28 18:27:13]

lgtm

[esprehn, 2014-10-28 18:29:12]

Committed patchset #3 (id:40001) manually as
d2c4163b85c39217c191c48f4732723681209f4a (presubmit successful).

[jamesr, 2014-11-01 00:07:59]

jamesr@chromium.org changed reviewers:
+ jamesr@chromium.org

[jamesr, 2014-11-01 00:07:59]

FYI this patch is going to be a no-op soon since we're going to consume a
network service built from chromium.  Please land this patch on the chromium
side.

[abarth-chromium, 2014-11-03 03:30:10]

abarth@chromium.org changed reviewers:
+ abarth@chromium.org

[abarth-chromium, 2014-11-03 03:30:11]

Ported to Chromium repo in https://codereview.chromium.org/697883003