Add a function triggering extension installed to ExtensionRegistryObserver

extensions/browser/extension_registry.cc

Index: extensions/browser/extension_registry.cc
diff --git a/extensions/browser/extension_registry.cc b/extensions/browser/extension_registry.cc
index ac6c274db6c13cbe21986b4f98ddc69165bda2b4..7a65c03fd40b5f66f34295bd51bff9f27a8ec19f 100644
--- a/extensions/browser/extension_registry.cc
+++ b/extensions/browser/extension_registry.cc
@@ -53,6 +53,16 @@ void ExtensionRegistry::TriggerOnUnloaded(
                     OnExtensionUnloaded(browser_context_, extension, reason));
 }
 
+void ExtensionRegistry::TriggerOnInstalled(const Extension* extension,
+                                           bool is_update,
+                                           const std::string& old_name) {
+  DCHECK(!GenerateInstalledExtensionsSet()->Contains(extension->id()));
+  FOR_EACH_OBSERVER(ExtensionRegistryObserver,
+                    observers_,
+                    OnExtensionWillBeInstalled(
+                        browser_context_, extension, is_update, old_name));
+}
+
 const Extension* ExtensionRegistry::GetExtensionById(const std::string& id,
                                                      int include_mask) const {
   std::string lowercase_id = StringToLowerASCII(id);