Remove //chrome dependency from ExtensionPrefs

chrome/browser/extensions/chrome_extensions_browser_client.cc

Index: chrome/browser/extensions/chrome_extensions_browser_client.cc
diff --git a/chrome/browser/extensions/chrome_extensions_browser_client.cc b/chrome/browser/extensions/chrome_extensions_browser_client.cc
index 67d76bd16bed8a6df3f8b6e7de7bab9062f58ccc..877eafddfcd4e0ce04fb3219bf2a668420615b56 100644
--- a/chrome/browser/extensions/chrome_extensions_browser_client.cc
+++ b/chrome/browser/extensions/chrome_extensions_browser_client.cc
@@ -10,6 +10,7 @@
 #include "chrome/browser/app_mode/app_mode_utils.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/extensions/activity_log/activity_log.h"
+#include "chrome/browser/extensions/api/content_settings/content_settings_service.h"
 #include "chrome/browser/extensions/api/preference/chrome_direct_setting.h"
 #include "chrome/browser/extensions/api/preference/preference_api.h"
 #include "chrome/browser/extensions/api/web_request/web_request_api.h"
@@ -238,4 +239,12 @@ void ChromeExtensionsBrowserClient::RegisterExtensionFunctions(
 #endif
 }
 
+void ChromeExtensionsBrowserClient::AddExtensionPrefsObservers(
+    content::BrowserContext* context,
+    ExtensionPrefs* prefs) const {
+  ContentSettingsService* content_settings =
+      ContentSettingsService::Get(context);
+  prefs->AddObserver(content_settings);
+}
+
 }  // namespace extensions