app_shell: Extract extension runtime data from ExtensionService

extensions/browser/extension_registry.h

Index: extensions/browser/extension_registry.h
diff --git a/extensions/browser/extension_registry.h b/extensions/browser/extension_registry.h
index d878e61e84db8ec44e56741cad14925dd997c038..89256e1583eb9f902eecec627febf5b588d9634f 100644
--- a/extensions/browser/extension_registry.h
+++ b/extensions/browser/extension_registry.h
@@ -9,6 +9,7 @@
 
 #include "base/compiler_specific.h"
 #include "base/memory/ref_counted.h"
+#include "base/observer_list.h"
 #include "components/browser_context_keyed_service/browser_context_keyed_service.h"
 #include "extensions/common/extension_set.h"
 
@@ -18,6 +19,7 @@ class BrowserContext;
 
 namespace extensions {
 class Extension;
+class ExtensionRegistryObserver;
 
 // ExtensionRegistry holds sets of the installed extensions for a given
 // BrowserContext. An incognito browser context and its master browser context
@@ -55,6 +57,14 @@ class ExtensionRegistry : public BrowserContextKeyedService {
     return blacklisted_extensions_;
   }
 
+  // The usual observer interface.
+  void AddObserver(ExtensionRegistryObserver* observer);
+  void RemoveObserver(ExtensionRegistryObserver* observer);
+
+  // Invokes the observer method OnExtensionUnloaded(). The extension must not
+  // be enabled at the time of the call.
+  void TriggerOnUnloaded(const Extension* extension);
+
   // Find an extension by ID using |include_mask| to pick the sets to search:
   //  * enabled_extensions()     --> ExtensionRegistry::ENABLED
   //  * disabled_extensions()    --> ExtensionRegistry::DISABLED
@@ -117,6 +127,8 @@ class ExtensionRegistry : public BrowserContextKeyedService {
   // un-blacklisted.
   ExtensionSet blacklisted_extensions_;
 
+  ObserverList<ExtensionRegistryObserver> observers_;
+
   DISALLOW_COPY_AND_ASSIGN(ExtensionRegistry);
 };