Create a cache file before mounting zip file.

Create a cache file before mounting zip file.

Previusly JavaScript send a request to create a cache file before mounting zip
file, but the code was recently removed.  This CL adds lines to create a cache
to the API for mouting a zip file.

BUG=419285
TEST=repro steps on the bug

Committed: https://crrev.com/cf841063b6b7cfbfb40945a75a72e592b3fe6169
Cr-Commit-Position: refs/heads/master@{#297622}

[hirono, 2014-10-01 09:20:53]

hirono@chromium.org changed reviewers:
+ kinaba@chromium.org

[hirono, 2014-10-01 09:20:53]

PTAL the CL? Thank you!

[kinaba, 2014-10-01 09:48:38]

On 2014/10/01 09:20:53, hirono wrote:
> PTAL the CL? Thank you!

lgtm. sorry i couldn't catch it in the previous review...

[hirono, 2014-10-01 09:56:22]

The CQ bit was checked by hirono@chromium.org

[hirono, 2014-10-01 09:56:52]

On 2014/10/01 09:48:38, kinaba wrote:
> On 2014/10/01 09:20:53, hirono wrote:
> > PTAL the CL? Thank you!
> 
> lgtm. sorry i couldn't catch it in the previous review...

Thank you very much!

[commit-bot: I haz the power, 2014-10-01 09:57:29]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/622513002/1

[commit-bot: I haz the power, 2014-10-01 10:32:51]

Committed patchset #1 (id:1) as b370a9c5f877bc50f0fb617f58954eabd9f297cc

[commit-bot: I haz the power, 2014-10-01 10:33:32]

Patchset 1 (id:??) landed as
https://crrev.com/cf841063b6b7cfbfb40945a75a72e592b3fe6169
Cr-Commit-Position: refs/heads/master@{#297622}