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

chrome/browser/extensions/declarative_user_script_master.h

Index: chrome/browser/extensions/declarative_user_script_master.h
diff --git a/chrome/browser/extensions/declarative_user_script_master.h b/chrome/browser/extensions/declarative_user_script_master.h
index f41545df0bac4a5cfc8cf6c89def08dd7fa02b48..e9af244cbe43e0ea46607b438231ddaadc974f53 100644
--- a/chrome/browser/extensions/declarative_user_script_master.h
+++ b/chrome/browser/extensions/declarative_user_script_master.h
@@ -6,26 +6,22 @@
 #define CHROME_BROWSER_EXTENSIONS_DECLARATIVE_USER_SCRIPT_MASTER_H_
 
 #include "base/scoped_observer.h"
-#include "chrome/browser/extensions/user_script_loader.h"
-#include "extensions/browser/extension_registry_observer.h"
-#include "extensions/common/extension.h"
+#include "chrome/browser/extensions/extension_user_script_loader.h"
 
 class Profile;
 
 namespace extensions {
 
-class ExtensionRegistry;
 class UserScript;
 
 // Manages declarative user scripts for a single extension. Owns a
 // UserScriptLoader to which file loading and shared memory management
 // operations are delegated, and provides an interface for adding, removing,
 // and clearing scripts.
-class DeclarativeUserScriptMaster : public ExtensionRegistryObserver {
+class DeclarativeUserScriptMaster {
  public:
-  DeclarativeUserScriptMaster(Profile* profile,
-                              const ExtensionId& extension_id);
-  ~DeclarativeUserScriptMaster() override;
+  DeclarativeUserScriptMaster(Profile* profile, const HostID& host_id);
+  ~DeclarativeUserScriptMaster();
 
   // Adds script to shared memory region. This may not happen right away if a
   // script load is in progress.
@@ -39,23 +35,15 @@
   // away if a script load is in progress.
   void ClearScripts();
 
-  const ExtensionId& extension_id() const { return extension_id_; }
+  const HostID& host_id() const { return host_id_; }
 
  private:
-  // ExtensionRegistryObserver implementation.
-  void OnExtensionUnloaded(content::BrowserContext* browser_context,
-                           const Extension* extension,
-                           UnloadedExtensionInfo::Reason reason) override;
-
-  // ID of extension that owns scripts that this component manages.
-  ExtensionId extension_id_;
+  // ID of host that owns scripts that this component manages.
+  HostID host_id_;
 
   // Script loader that handles loading contents of scripts into shared memory
   // and notifying renderers of script updates.
-  UserScriptLoader loader_;
-
-  ScopedObserver<ExtensionRegistry, ExtensionRegistryObserver>
-      extension_registry_observer_;
+  ExtensionUserScriptLoader loader_;
 
   DISALLOW_COPY_AND_ASSIGN(DeclarativeUserScriptMaster);
 };