[Mojo] Fix the namespace for HandleWrapper

[Mojo] Fix the namespace for HandleWrapper

The HandleWrapper is part of the Mojo JavaScript bindings, not part of the
underlying gin library. For some reason HandleWrapper and HandleCloseObserver
were declared in the gin namespace, which is incorrect. This CL moves them to
the mojo::js namespace, which is correct.

R=hansmuller@chromium.org

Committed: https://crrev.com/e06d7eb4be3ac14834c16715718150a04c93ef53
Cr-Commit-Position: refs/heads/master@{#299218}

[hansmuller, 2014-10-10 23:04:26]

This patch LGTM.

[abarth-chromium, 2014-10-11 00:05:06]

The CQ bit was checked by abarth@chromium.org

[commit-bot: I haz the power, 2014-10-11 00:06:32]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/651523002/1

[commit-bot: I haz the power, 2014-10-11 00:21:19]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2014-10-11 00:21:57]

Patchset 1 (id:??) landed as
https://crrev.com/e06d7eb4be3ac14834c16715718150a04c93ef53
Cr-Commit-Position: refs/heads/master@{#299218}