Makes Env thread local

Makes Env thread local

This will enable aura to be used on multiple threads.

BUG=none
TEST=none
R=ben@chromium.org

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=270330

[Ben Goodger (Google), 2014-05-13 21:40:57]

lgtm

[sky, 2014-05-13 21:44:19]

The CQ bit was checked by sky@chromium.org

[commit-bot: I haz the power, 2014-05-13 21:45:22]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/sky@chromium.org/285793002/1

[commit-bot: I haz the power, 2014-05-14 00:57:53]

FYI, CQ is re-trying this CL (attempt #1).
Please consider checking whether the failures are real,
and report flakes to chrome-troopers@google.com.
The failing builders are:
  android_aosp on tryserver.chromium
(http://build.chromium.org/p/tryserver.chromium/builders/android_aosp/builds/7...)

[commit-bot: I haz the power, 2014-05-14 01:30:13]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2014-05-14 01:30:14]

Try jobs failed on following builders:
  android_aosp on tryserver.chromium
(http://build.chromium.org/p/tryserver.chromium/builders/android_aosp/builds/7...)

[sky, 2014-05-14 02:41:49]

The CQ bit was checked by sky@chromium.org

[commit-bot: I haz the power, 2014-05-14 02:42:57]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/sky@chromium.org/285793002/1

[commit-bot: I haz the power, 2014-05-14 02:47:53]

FYI, CQ is re-trying this CL (attempt #1).
Please consider checking whether the failures are real,
and report flakes to chrome-troopers@google.com.
The failing builders are:
  android_aosp on tryserver.chromium
(http://build.chromium.org/p/tryserver.chromium/builders/android_aosp/builds/7...)

[commit-bot: I haz the power, 2014-05-14 02:51:35]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2014-05-14 02:51:35]

Try jobs failed on following builders:
  android_aosp on tryserver.chromium
(http://build.chromium.org/p/tryserver.chromium/builders/android_aosp/builds/7...)

[sky, 2014-05-14 02:58:04]

The CQ bit was checked by sky@chromium.org

[commit-bot: I haz the power, 2014-05-14 02:59:54]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/sky@chromium.org/285793002/1

[commit-bot: I haz the power, 2014-05-14 03:04:56]

FYI, CQ is re-trying this CL (attempt #1).
Please consider checking whether the failures are real,
and report flakes to chrome-troopers@google.com.
The failing builders are:
  android_aosp on tryserver.chromium
(http://build.chromium.org/p/tryserver.chromium/builders/android_aosp/builds/7...)

[commit-bot: I haz the power, 2014-05-14 04:06:54]

Change committed as 270330