Add PNACL_CACHE cache backend type, and allow larger files for this type.

Add PNACL_CACHE cache backend type, and allow larger files for this type.

PnaCl's translation cache is currently using the DISK_CACHE backend,
but we don't want to mix the UMA statistics for these caches. Also,
because we expect PNaCl's cache to have a small number of files, which
will be much larger than most HTTP cache files, we remove the restriction
that files can take up no more than 1/8 of the cache. For machines with
little available disk space (and thus small caches), this may mean the
difference between being able to store any files in the cache, or not.

R=rvargas@chromium.org,jvoung@chromium.org
BUG=none
TEST= unit_tests PnaclTranslationCacheTest.* (and no net_unittests break)

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=224176

[Derek Schuff, 2013-09-18 18:17:29]

Ricardo: A couple of the other backend types run the backend unit tests a
separate time specifically for that type. Do you think it's worth doing that
here also, even though the changes are so minimal?

[rvargas (doing something else), 2013-09-18 19:45:43]

net lGTM

No, I don't think there is value adding specific DiskCache tests.

[jvoung (off chromium), 2013-09-18 20:28:59]

lgtm

[commit-bot: I haz the power, 2013-09-18 23:49:04]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/dschuff@chromium.org/24208003/1

[commit-bot: I haz the power, 2013-09-18 23:54:50]

Retried try job too often on chromium_presubmit for step(s) presubmit
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=chromium_p...

[commit-bot: I haz the power, 2013-09-19 15:49:36]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/dschuff@chromium.org/24208003/1

[commit-bot: I haz the power, 2013-09-19 18:52:59]

Change committed as 224176

[rvargas (doing something else), 2013-09-23 17:37:03]

BTW, now we need descriptions for the new batch of histograms...