Move some dependencies of ExtensionService down to extensions.

These files do not have any dependencies to the rest of chrome so can
move down immediately.

TBR=miket, sky
BUG=298537

Review URL: https://codereview.chromium.org/82773002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@237299 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 237299
Support cloud policy for extensions on the desktop platforms.

The ComponentCloudPolicyService manages the storage and updates of cloud policy
for chrome components, such as extensions. This component is now managed by
the CloudPolicyManager, so that the UserCloudPolicyManagers can share its
lifetime logic.

Later it may be used by the DeviceCloudPolicyManager and the local accounts
policy manager.

This feature is still disabled by default behind a flag.

BUG=108992

Review URL: https://codereview.chromium.org/79023002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@237300 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 237300