Revert of Remove deprecated extension notifications from ProcessManager

extensions/browser/process_manager.cc

Index: extensions/browser/process_manager.cc
diff --git a/extensions/browser/process_manager.cc b/extensions/browser/process_manager.cc
index fd7a545c1d397906a928c8eca6103a911b49bb0d..e6beddbb891fcd56bf272cd5e58494f172773b20 100644
--- a/extensions/browser/process_manager.cc
+++ b/extensions/browser/process_manager.cc
@@ -229,10 +229,13 @@
       devtools_callback_(base::Bind(&ProcessManager::OnDevToolsStateChanged,
                                     base::Unretained(this))),
       last_background_close_sequence_id_(0),
-      weak_ptr_factory_(this),
-      extension_registry_observer_(this) {
-  extension_registry_observer_.Add(ExtensionRegistry::Get(original_context));
+      weak_ptr_factory_(this) {
   registrar_.Add(this, chrome::NOTIFICATION_EXTENSIONS_READY,
+                 content::Source<BrowserContext>(original_context));
+  registrar_.Add(this,
+                 chrome::NOTIFICATION_EXTENSION_LOADED_DEPRECATED,
+                 content::Source<BrowserContext>(original_context));
+  registrar_.Add(this, chrome::NOTIFICATION_EXTENSION_UNLOADED_DEPRECATED,
                  content::Source<BrowserContext>(original_context));
   registrar_.Add(this, chrome::NOTIFICATION_EXTENSION_HOST_DESTROYED,
                  content::Source<BrowserContext>(context));
@@ -657,6 +660,33 @@
       break;
     }
 
+    case chrome::NOTIFICATION_EXTENSION_LOADED_DEPRECATED: {
+      BrowserContext* context = content::Source<BrowserContext>(source).ptr();
+      ExtensionSystem* system = ExtensionSystem::Get(context);
+      if (system->ready().is_signaled()) {
+        // The extension system is ready, so create the background host.
+        const Extension* extension =
+            content::Details<const Extension>(details).ptr();
+        CreateBackgroundHostForExtensionLoad(this, extension);
+      }
+      break;
+    }
+
+    case chrome::NOTIFICATION_EXTENSION_UNLOADED_DEPRECATED: {
+      const Extension* extension =
+          content::Details<UnloadedExtensionInfo>(details)->extension;
+      for (ExtensionHostSet::iterator iter = background_hosts_.begin();
+           iter != background_hosts_.end(); ++iter) {
+        ExtensionHost* host = *iter;
+        if (host->extension_id() == extension->id()) {
+          CloseBackgroundHost(host);
+          break;
+        }
+      }
+      UnregisterExtension(extension->id());
+      break;
+    }
+
     case chrome::NOTIFICATION_EXTENSION_HOST_DESTROYED: {
       ExtensionHost* host = content::Details<ExtensionHost>(details).ptr();
       if (background_hosts_.erase(host)) {
@@ -728,30 +758,6 @@
     default:
       NOTREACHED();
   }
-}
-
-void ProcessManager::OnExtensionLoaded(content::BrowserContext* browser_context,
-                                       const Extension* extension) {
-  if (ExtensionSystem::Get(browser_context)->ready().is_signaled()) {
-    // The extension system is ready, so create the background host.
-    CreateBackgroundHostForExtensionLoad(this, extension);
-  }
-}
-
-void ProcessManager::OnExtensionUnloaded(
-    content::BrowserContext* browser_context,
-    const Extension* extension,
-    UnloadedExtensionInfo::Reason reason) {
-  for (ExtensionHostSet::iterator iter = background_hosts_.begin();
-       iter != background_hosts_.end();
-       ++iter) {
-    ExtensionHost* host = *iter;
-    if (host->extension_id() == extension->id()) {
-      CloseBackgroundHost(host);
-      break;
-    }
-  }
-  UnregisterExtension(extension->id());
 }
 
 void ProcessManager::OnDevToolsStateChanged(