Add ExtensionsApiClient interface, use it in the storage API SettingsFrontend

chrome/browser/extensions/api/storage/policy_value_store.cc

Index: chrome/browser/extensions/api/storage/policy_value_store.cc
diff --git a/chrome/browser/extensions/api/storage/policy_value_store.cc b/chrome/browser/extensions/api/storage/policy_value_store.cc
index 9691e2bf01c832a43b7e6db4d6c8710d2d7858f6..9560c9b3b9d08796017f7a7cd9e2351dc26fa9fb 100644
--- a/chrome/browser/extensions/api/storage/policy_value_store.cc
+++ b/chrome/browser/extensions/api/storage/policy_value_store.cc
@@ -6,12 +6,12 @@
 
 #include "base/logging.h"
 #include "base/values.h"
-#include "chrome/browser/extensions/api/storage/settings_namespace.h"
 #include "chrome/browser/value_store/value_store_change.h"
 #include "chrome/browser/value_store/value_store_util.h"
 #include "components/policy/core/common/policy_map.h"
 #include "components/policy/core/common/policy_types.h"
 #include "content/public/browser/browser_thread.h"
+#include "extensions/browser/api/storage/settings_namespace.h"
 
 using content::BrowserThread;