Reland of https://codereview.chromium.org/62713003/ - the original patch broke the Google Chrome OS official builder due to a missing dependency on the extensions api target in extensions/extensions.gyp.
* 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
TBR=miket@chromium.org
Review URL: https://codereview.chromium.org/67253003
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@234149 0039d316-1c4b-4281-b951-d872f2087c98