Revert of Remove webkit's ResourceLoaderBridge interface.

Revert of Remove webkit's ResourceLoaderBridge interface. (https://codereview.chromium.org/226273005/)

Reason for revert:
Looks like it broke LSan bots:

http://build.chromium.org/p/chromium.memory/builders/Linux%20ASan%20LSan%20Tests%20%282%29/builds/2229
TBR=jam
NOTREECHECKS=true
NOTRY=true

Original issue's description:
> Remove webkit's ResourceLoaderBridge interface.
> 
> ResourceLoaderBridge was originally created to bridge code in //webkit that
> talked to WebURLLoaderImpl (which talked to Blink) with code in
> ResourceDispatcher in content which used IPC. Now that WebURLLoaderImpl
> is in content/child, we don't need this interface anymore.
> 
> As requested by John in -
> https://codereview.chromium.org/186193005/diff/1/content/public/child/resource_loader_bridge.h#newcode42
> 
> BUG=265753, 338338, 237249
> TEST=content_unittests
> R=jam@chromium.org
> TBR=darin
> 
> Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=267947

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=267999

[DaleCurtis, 2014-05-03 01:50:01]

Created Revert of Remove webkit's ResourceLoaderBridge interface.

[commit-bot: I haz the power, 2014-05-03 01:50:35]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/dalecurtis@chromium.org/267973002/1

[commit-bot: I haz the power, 2014-05-03 01:50:35]

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

[commit-bot: I haz the power, 2014-05-03 01:50:36]

No LGTM from a valid reviewer yet. Only full committers are accepted.
Even if an LGTM may have been provided, it was from a non-committer or
a provisional committer, _not_ a full super star committer.
See http://www.chromium.org/getting-involved/become-a-committer
Note that this has nothing to do with OWNERS files.

[DaleCurtis, 2014-05-03 01:52:51]

The CQ bit was checked by dalecurtis@chromium.org

[commit-bot: I haz the power, 2014-05-03 01:54:02]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/dalecurtis@chromium.org/267973002/1

[DaleCurtis, 2014-05-03 01:54:58]

The CQ bit was unchecked by dalecurtis@chromium.org

[DaleCurtis, 2014-05-03 01:55:02]

The CQ bit was checked by dalecurtis@chromium.org

[commit-bot: I haz the power, 2014-05-03 01:55:51]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/dalecurtis@chromium.org/267973002/1

[DaleCurtis, 2014-05-03 01:56:26]

Stupid revert is trying to CQ, added appropriate commit message-fu.

[commit-bot: I haz the power, 2014-05-03 01:57:12]

Change committed as 267999

[tfarina, 2014-05-03 02:04:59]

OK, thanks.

Sorry for the breakage.