Make HPACK static table static and immutable.

Make HPACK static table static and immutable.

Create HpackStaticTable singleton class, so that every HPACK context can share
a constant instance of the static table.

This lands server change 74862865 by bnc.

BUG=400336
Committed: https://crrev.com/d4ec60089740b0613792208ee57ff2ffccb2b6f5
Cr-Commit-Position: refs/heads/master@{#293710}

[Bence, 2014-09-05 21:59:55]

bnc@chromium.org changed reviewers:
+ rch@chromium.org

[Bence, 2014-09-05 21:59:55]

PTAL.  Thank you.

[Ryan Hamilton, 2014-09-05 22:08:36]

lgtm

[Bence, 2014-09-08 11:50:34]

The CQ bit was checked by bnc@chromium.org

[commit-bot: I haz the power, 2014-09-08 11:51:39]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/bnc@chromium.org/549583003/1

[commit-bot: I haz the power, 2014-09-08 12:37:24]

Committed patchset #1 (id:1) as d40b00e7f2fa249e4c04784e7ccd1bd2f5572688

[commit-bot: I haz the power, 2014-09-10 03:45:49]

Patchset 1 (id:??) landed as
https://crrev.com/d4ec60089740b0613792208ee57ff2ffccb2b6f5
Cr-Commit-Position: refs/heads/master@{#293710}