Revert 233956 "Move ExtensionProcessManager to src/extensions, p..."

Compile error, runtime.h has moved?

> Move ExtensionProcessManager to src/extensions, part 4
> 
> * Move c/b/extensions/extension_process_manager.h to
>   extensions/browser/process_manager.h
> * Rename ExtensionsProcessManager to ProcessManager
> * Place it in the "extensions" namespace
> 
> BUG=313481
> TEST=browser_tests, unit_tests
> R=miket@chromium.org
> TBR=sky@chromium.org for mechanical header file move affecting chrome/browser/
> 
> Review URL: https://codereview.chromium.org/62713003

TBR=jamescook@chromium.org

Review URL: https://codereview.chromium.org/66213006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@233959 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 233959