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..7ad39180022a38cdbb5e5f53dbb2f4293d196e3b 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::TriggerOnWillBeInstalled(const Extension* extension,
+                                                 bool is_update,
+                                                 const std::string& old_name) {
+  DCHECK(!GenerateInstalledExtensionsSet()->Contains(extension->id()));

[limasdf, 2014/05/17 13:15:10]

I'm going to remove this DCHECK.
Because when service reloads extension by |ReloadExtension|,
service just make the existing extension as DISABLED status. and then send
INSTALLED notification.

I catched this issue while running unittest.
https://code.google.com/p/chromium/codesearch#chromium/src/chrome/browser/ext...

+  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);