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/chrome_extensions_browser_client.cc b/chrome/browser/extensions/chrome_extensions_browser_client.cc
index 5ed2495..6928e29 100644
--- a/chrome/browser/extensions/chrome_extensions_browser_client.cc
+++ b/chrome/browser/extensions/chrome_extensions_browser_client.cc
@@ -9,7 +9,6 @@
 #include "chrome/browser/app_mode/app_mode_utils.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/extensions/chrome_app_sorting.h"
-#include "chrome/browser/extensions/extension_prefs.h"
 #include "chrome/browser/extensions/extension_system.h"
 #include "chrome/browser/extensions/extension_system_factory.h"
 #include "chrome/browser/profiles/profile.h"
@@ -20,6 +19,7 @@
 #include "chrome/common/chrome_switches.h"
 #include "chrome/common/chrome_version_info.h"
 #include "chrome/common/pref_names.h"
+#include "extensions/browser/extension_prefs.h"
 #include "extensions/browser/pref_names.h"
 
 #if defined(OS_CHROMEOS)