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

chrome/browser/extensions/declarative_user_script_master.cc

Index: chrome/browser/extensions/declarative_user_script_master.cc
diff --git a/chrome/browser/extensions/declarative_user_script_master.cc b/chrome/browser/extensions/declarative_user_script_master.cc
index fccd01150491ef3d4b31d2305112e28652aa7c52..40fc511dd964ec23196d31fd6677979381963d22 100644
--- a/chrome/browser/extensions/declarative_user_script_master.cc
+++ b/chrome/browser/extensions/declarative_user_script_master.cc
@@ -7,30 +7,18 @@
 #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) {