Add a function triggering extension installed to ExtensionRegistryObserver

extensions/browser/extension_registry.h

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef EXTENSIONS_BROWSER_EXTENSION_REGISTRY_H_
 #define EXTENSIONS_BROWSER_EXTENSION_REGISTRY_H_
 
 #include <string>
 
 #include "base/compiler_specific.h"
@@ skipping 56 matching lines @@
 
   // Invokes the observer method OnExtensionLoaded(). The extension must be
   // enabled at the time of the call.
   void TriggerOnLoaded(const Extension* extension);
 
   // Invokes the observer method OnExtensionUnloaded(). The extension must not
   // be enabled at the time of the call.
   void TriggerOnUnloaded(const Extension* extension,
                          UnloadedExtensionInfo::Reason reason);
 
+  // Invokes the observer method OnExtensionWillBeInstalled(). The extension
+  // must not be tracked at the time of the call, and the caller should ensure
+  // to track it afterward.

[not at google - send to devlin, 2014/05/20 18:27:12]

This comment is wrong again. It needs to take into account |is_update|. How
about:

If this is a fresh install then |is_update| is false and there must not be any
installed extension with |extension|'s ID. If this is an update then |is_update|
is true and must be an installed extension with |extension|'s ID, and |old_name|
must be non-empty.

[limasdf, 2014/05/21 15:35:08]

Done.

+  void TriggerOnWillBeInstalled(const Extension* extension,
+                                bool is_update,
+                                const std::string& old_name);
+
   // Find an extension by ID using |include_mask| to pick the sets to search:
   //  * enabled_extensions()     --> ExtensionRegistry::ENABLED
   //  * disabled_extensions()    --> ExtensionRegistry::DISABLED
   //  * terminated_extensions()  --> ExtensionRegistry::TERMINATED
   //  * blacklisted_extensions() --> ExtensionRegistry::BLACKLISTED
   // Returns NULL if the extension is not found in the selected sets.
   const Extension* GetExtensionById(const std::string& id,
                                     int include_mask) const;
 
   // Adds the specified extension to the enabled set. The registry becomes an
@@ skipping 52 matching lines @@
   ObserverList<ExtensionRegistryObserver> observers_;
 
   content::BrowserContext* const browser_context_;
 
   DISALLOW_COPY_AND_ASSIGN(ExtensionRegistry);
 };
 
 }  // namespace extensions
 
 #endif  // EXTENSIONS_BROWSER_EXTENSION_REGISTRY_H_