Move ExtensionPrefs and friends to extensions/ directory.

Move ExtensionPrefs and related classes from
chrome/browser/extensions/ to the top-level extensions/
directory. The following classes are moved:

ExtensionPrefStore
ExtensionPrefValueMap
ExtensionPrefValueMapFactory
ExtensionPrefs
ExtensionPrefsFactory
ExtensionScopedPref

The TestExtensionPrefs helper class and the
ExtensionPrefsTest unit tests remain in
chrome/browser/extensions, since TestExtensionPrefs has a
dependency on Chrome's PrefServiceSyncable that seems like it
will be difficult to break (more explanation at
https://codereview.chromium.org/108643002/).

BUG=313284
[email protected],[email protected]

Review URL: https://codereview.chromium.org/46853004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@246373 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/chrome/browser/extensions/webstore_standalone_installer.cc b/chrome/browser/extensions/webstore_standalone_installer.cc
index 9f5e41a6..48661896 100644
--- a/chrome/browser/extensions/webstore_standalone_installer.cc
+++ b/chrome/browser/extensions/webstore_standalone_installer.cc
@@ -8,12 +8,12 @@
 #include "chrome/browser/extensions/crx_installer.h"
 #include "chrome/browser/extensions/extension_install_prompt.h"
 #include "chrome/browser/extensions/extension_install_ui.h"
-#include "chrome/browser/extensions/extension_prefs.h"
 #include "chrome/browser/extensions/extension_service.h"
 #include "chrome/browser/extensions/extension_system.h"
 #include "chrome/browser/extensions/webstore_data_fetcher.h"
 #include "chrome/browser/profiles/profile.h"
 #include "content/public/browser/web_contents.h"
+#include "extensions/browser/extension_prefs.h"
 #include "extensions/common/extension.h"
 #include "url/gurl.h"