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 e9af244cbe43e0ea46607b438231ddaadc974f53..f41545df0bac4a5cfc8cf6c89def08dd7fa02b48 100644
--- a/chrome/browser/extensions/declarative_user_script_master.h
+++ b/chrome/browser/extensions/declarative_user_script_master.h
@@ -6,22 +6,26 @@
 #define CHROME_BROWSER_EXTENSIONS_DECLARATIVE_USER_SCRIPT_MASTER_H_
 
 #include "base/scoped_observer.h"
-#include "chrome/browser/extensions/extension_user_script_loader.h"
+#include "chrome/browser/extensions/user_script_loader.h"
+#include "extensions/browser/extension_registry_observer.h"
+#include "extensions/common/extension.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 {
+class DeclarativeUserScriptMaster : public ExtensionRegistryObserver {
  public:
-  DeclarativeUserScriptMaster(Profile* profile, const HostID& host_id);
-  ~DeclarativeUserScriptMaster();
+  DeclarativeUserScriptMaster(Profile* profile,
+                              const ExtensionId& extension_id);
+  ~DeclarativeUserScriptMaster() override;
 
   // Adds script to shared memory region. This may not happen right away if a
   // script load is in progress.
@@ -35,15 +39,23 @@ class DeclarativeUserScriptMaster {
   // away if a script load is in progress.
   void ClearScripts();
 
-  const HostID& host_id() const { return host_id_; }
+  const ExtensionId& extension_id() const { return extension_id_; }
 
  private:
-  // ID of host that owns scripts that this component manages.
-  HostID host_id_;
+  // 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_;
 
   // Script loader that handles loading contents of scripts into shared memory
   // and notifying renderers of script updates.
-  ExtensionUserScriptLoader loader_;
+  UserScriptLoader loader_;
+
+  ScopedObserver<ExtensionRegistry, ExtensionRegistryObserver>
+      extension_registry_observer_;
 
   DISALLOW_COPY_AND_ASSIGN(DeclarativeUserScriptMaster);
 };