Revert of Revert of Revert of Reland factor out window proxy management

Revert of Revert of Revert of Reland factor out window proxy management portions of ScriptController. (patchset #3 id:250001 of https://codereview.chromium.org/854453003/)

Reason for revert:
Needed data gathered, so reverting to reduce number of crash dumps.

Original issue's description:
> Reland factor out window proxy management portions of ScriptController.
> 
> Right now, ScriptController is in charge of initializing window proxies,
> clearing them for navigation/close, and maintaining a mapping of worlds
> to window proxies. However, ScriptController is LocalFrame-specific, and
> RemoteFrame also needs to expose a DOMWindow for scripting purposes. To
> share code between the two, the window proxy management has been moved
> out of ScriptController, leaving only LocalFrame-specific logic such as
> wrapping NPObject for plugins or script evaluation.
> 
> Eventually, RemoteFrame will also embed a WindowProxyManager, and
> WindowProxyManager will be extended to allow it be passed between frames
> when transitioning between local and remote frames.
> 
> For integration with devtools, WindowProxyManager still contains some
> LocalFrame-specific code.
> 
> BUG=425623
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=188574

TBR=haraken@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=425623

[dcheng, 2015-01-20 18:31:02]

Created Revert of Revert of Revert of Reland factor out window proxy management
portions of ScriptController.

[commit-bot: I haz the power, 2015-01-20 18:32:06]

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

[dcheng, 2015-01-20 18:38:47]

The CQ bit was checked by dcheng@chromium.org

[commit-bot: I haz the power, 2015-01-20 18:40:02]

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

[haraken, 2015-01-20 23:38:21]

LGTM