Remove obsolete code path that uses double as time stamp for metadata

Remove obsolete code path that uses double as time stamp for metadata in the HTTP cache.

This is part 4/4 of a clean up to switch to int64 time stamps when caching metadata. The background to this is that converting int64 time stamps to double and back to int64 is lossy and causes false time stamp mismatches.

BUG=453298
Committed: https://crrev.com/e88c0f1cd021ba15ab55dfdd363c8d8552514bd2
Cr-Commit-Position: refs/heads/master@{#317517}

[Yang, 2015-02-18 09:36:55]

yangguo@chromium.org changed reviewers:
+ davidben@chromium.org

[Yang, 2015-02-18 09:47:24]

Please take a look. This is part of a series of CLs between blink and chromium.

Part 1/4: https://codereview.chromium.org/938643002/
Part 2/4: https://codereview.chromium.org/935963002/
Part 3/4: https://codereview.chromium.org/940443002/
Part 4/4: https://codereview.chromium.org/935983002/

[davidben, 2015-02-18 18:52:15]

(Going by review comments on parts 1 and 2, I expect this CL might end up
changing somewhat, since it's a cleanup pass. I'll pause on it until the first
two have settled.)

[Yang, 2015-02-19 08:41:22]

On 2015/02/18 18:52:15, David Benjamin wrote:
> (Going by review comments on parts 1 and 2, I expect this CL might end up
> changing somewhat, since it's a cleanup pass. I'll pause on it until the first
> two have settled.)

Updated to reflect changes in part 2.

[davidben, 2015-02-19 21:40:46]

lgtm

[Yang, 2015-02-20 10:14:14]

New patchsets have been uploaded after l-g-t-m from davidben@chromium.org

[Yang, 2015-02-20 10:16:19]

Patchset #4 (id:60001) has been deleted

[Yang, 2015-02-21 19:22:29]

The CQ bit was checked by yangguo@chromium.org

[commit-bot: I haz the power, 2015-02-21 19:23:01]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/935983002/80001

[commit-bot: I haz the power, 2015-02-21 21:01:59]

Committed patchset #4 (id:80001)

[commit-bot: I haz the power, 2015-02-21 21:02:31]

Patchset 4 (id:??) landed as
https://crrev.com/e88c0f1cd021ba15ab55dfdd363c8d8552514bd2
Cr-Commit-Position: refs/heads/master@{#317517}