1. A method comprising: obtaining in a computing system a resource list over a network connection, wherein the resource list identifies resources associated with an application, the application providing functionality to a user of the application when the application is executed using the resources identified in the resource list; obtaining the resources through communications over the network connection and storing the resources in local storage, the local storage being on the computing system and accessible by the computing system without the network connection, wherein the resources include a native code module that includes binary code that can run directly on a central processing unit of the computing system; loading the application in a web browser on the computing system; loading the native code module into a secure runtime environment on the computing system; executing the web browser and the application on the computing system independently of the network connection, including executing the binary code of the native code module in the secure runtime environment directly on the central processing unit of the computing system on which the web browser and the application are executing, wherein the binary code is executed on behalf of the application to provide to a user of the application one or more features of the functionality of the application; and validating the native code module, wherein the validating includes determining that the set of instructions in the native code module do not include any restricted instructions and do not access restricted features of the computing system, prior to executing the native code module in the secure runtime environment.