Revert of Revert of Introduce HostID and de-couple Extensions from "script injection System" [browser side]

chrome/browser/extensions/declarative_user_script_master.cc

 // Copyright 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/declarative_user_script_master.h"
 
 #include <set>
 
 #include "chrome/browser/profiles/profile.h"
-#include "extensions/browser/extension_registry.h"
 
 namespace extensions {
 
-DeclarativeUserScriptMaster::DeclarativeUserScriptMaster(
-    Profile* profile,
-    const ExtensionId& extension_id)
-    : extension_id_(extension_id),
+DeclarativeUserScriptMaster::DeclarativeUserScriptMaster(Profile* profile,
+                                                         const HostID& host_id)
+    : host_id_(host_id),
       loader_(profile,
-              extension_id,
-              false /* listen_for_extension_system_loaded */),
-      extension_registry_observer_(this) {
-  extension_registry_observer_.Add(ExtensionRegistry::Get(profile));
+              host_id,
+              false /* listen_for_extension_system_loaded */) {
 }
 
 DeclarativeUserScriptMaster::~DeclarativeUserScriptMaster() {
 }
 
-void DeclarativeUserScriptMaster::OnExtensionUnloaded(
-    content::BrowserContext* browser_context,
-    const Extension* extension,
-    UnloadedExtensionInfo::Reason reason) {
-  if (extension_id_ == extension->id())
-    ClearScripts();
-}
-
 void DeclarativeUserScriptMaster::AddScript(const UserScript& script) {
   std::set<UserScript> set;
   set.insert(script);
   loader_.AddScripts(set);
 }
 
 void DeclarativeUserScriptMaster::RemoveScript(const UserScript& script) {
   std::set<UserScript> set;
   set.insert(script);
   loader_.RemoveScripts(set);
 }
 
 void DeclarativeUserScriptMaster::ClearScripts() {
   loader_.ClearScripts();
 }
 
 }  // namespace extensions