Handle integer -0 as 0 in extensions

Handle integer -0 as 0 in extensions

-0 is treated as double 0.0f in V8. This makes GetAsInteger()
return -0 is not an integer type. Extension APIs with integer parameters
will fail to get the value using GetAsInteger(). This CL convert integer
-0 to integer 0.

BUG=471011
Committed: https://crrev.com/8e575f12fb732a497e0e9fc34e1e739621cecf3c
Cr-Commit-Position: refs/heads/master@{#329860}

[qiankun, 2015-05-14 10:00:23]

qiankun.miao@intel.com changed reviewers:
+ rockot@chromium.org

[qiankun, 2015-05-14 10:00:24]

PTAL.

[Ken Rockot(use gerrit already), 2015-05-14 14:52:24]

lgtm

[qiankun, 2015-05-14 15:18:32]

The CQ bit was checked by qiankun.miao@intel.com

[commit-bot: I haz the power, 2015-05-14 15:19:00]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1126983009/1

[commit-bot: I haz the power, 2015-05-14 16:52:00]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-05-14 16:53:32]

Patchset 1 (id:??) landed as
https://crrev.com/8e575f12fb732a497e0e9fc34e1e739621cecf3c
Cr-Commit-Position: refs/heads/master@{#329860}