MD Settings: clarify "controlled by" logic

chrome/browser/extensions/settings_api_helpers.cc

 // Copyright (c) 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/extensions/settings_api_helpers.h"
 
 #include "chrome/browser/extensions/api/preference/preference_api.h"
 #include "chrome/common/pref_names.h"
+#include "chrome/common/url_constants.h"
 #include "components/proxy_config/proxy_config_pref_names.h"
 #include "components/search_engines/search_engines_pref_names.h"
+#include "content/public/browser/browser_url_handler.h"
 #include "extensions/browser/extension_pref_value_map.h"
 #include "extensions/browser/extension_pref_value_map_factory.h"
 #include "extensions/browser/extension_registry.h"
+#include "extensions/common/constants.h"
 #include "extensions/common/extension_set.h"
+#include "url/gurl.h"
 
 namespace extensions {
 
 namespace {
 
 // Returns which |extension| (if any) is overriding a particular |type| of
 // setting.
 const Extension* FindOverridingExtension(
     content::BrowserContext* browser_context,
     SettingsApiOverrideType type) {
@@ skipping 39 matching lines @@
   return NULL;
 }
 
 }  // namespace
 
 const Extension* GetExtensionOverridingHomepage(
     content::BrowserContext* browser_context) {
   return FindOverridingExtension(browser_context, BUBBLE_TYPE_HOME_PAGE);
 }
 
+const Extension* GetExtensionOverridingNewTabPage(
+    content::BrowserContext* browser_context) {
+  GURL ntp_url(chrome::kChromeUINewTabURL);
+  bool ignored;
+  content::BrowserURLHandler::GetInstance()->RewriteURLIfNecessary(
+      &ntp_url, browser_context, &ignored);
+  if (ntp_url.SchemeIs(kExtensionScheme)) {
+    return ExtensionRegistry::Get(browser_context)->GetExtensionById(
+        ntp_url.host(), ExtensionRegistry::ENABLED);
+  }
+  return nullptr;
+}
+
 const Extension* GetExtensionOverridingStartupPages(
     content::BrowserContext* browser_context) {
   return FindOverridingExtension(browser_context, BUBBLE_TYPE_STARTUP_PAGES);
 }
 
 const Extension* GetExtensionOverridingSearchEngine(
     content::BrowserContext* browser_context) {
   return FindOverridingExtension(browser_context, BUBBLE_TYPE_SEARCH_ENGINE);
 }
 
 const Extension* GetExtensionOverridingProxy(
     content::BrowserContext* browser_context) {
   ExtensionPrefValueMap* extension_prefs_value_map =
       ExtensionPrefValueMapFactory::GetForBrowserContext(browser_context);
   if (!extension_prefs_value_map)
     return NULL;  // Can be null during testing.
   std::string extension_id =
       extension_prefs_value_map->GetExtensionControllingPref(
           proxy_config::prefs::kProxy);
   if (extension_id.empty())
     return NULL;
   return ExtensionRegistry::Get(browser_context)->GetExtensionById(
       extension_id, ExtensionRegistry::ENABLED);
 }
 
 }  // namespace extensions