Revert of Extract RuntimeEventRouter from extensions Runtime API

Revert of Extract RuntimeEventRouter from extensions Runtime API (https://codereview.chromium.org/206613005/)

Reason for revert:
After talking to yoz@ and rockot@ I don't
think we want to extract the runtime implementation to src/extensions. It's got too much Chrome-specific stuff, and for app_shell we really need app_runtime and not runtime.


Original issue's description:
> Extract RuntimeEventRouter from extensions Runtime API
> 
> Another step toward moving the runtime API to src/extensions so it can be
> used by app_shell.
> 
> BUG=354552
> TEST=browser_tests ExtensionApi*:*Runtime*
> TBR=xiyuan@chromium.org for header file move touching chrome/browser/chromeos/app_mode
> 
> Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=259477

TBR=yoz@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=354552
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=259755

[James Cook, 2014-03-27 00:08:05]

Created Revert of Extract RuntimeEventRouter from extensions Runtime API

[commit-bot: I haz the power, 2014-03-27 00:08:30]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/jamescook@chromium.org/213313007/1

[commit-bot: I haz the power, 2014-03-27 00:14:47]

Change committed as 259755