1. One or more computer-readable storage media storing computer-executable instructions that, when executed, cause one or more processors to perform acts comprising: receiving a request to execute a first application on a computing device; determining if the first application is directly executable on the computing device; executing the first application at least partly in response to determining that the first application is directly executable on the computing device; and at least partly in response to determining that the first application is not directly executable on the computing device: determining if the first application specifies a second application to be executed prior to executing the first application; executing the second application on the computing device at least partly in response to determining that the first application specifies the second application to be executed prior to executing the first application; executing a default application on the computing device at least partly in response to determining that the first application does not specify the second application to be executed prior to executing the first application; and executing library components to provide system services, wherein the library components execute inside an isolated container of the second application if the first application specified the second application, or an isolated container of the default application if the first application did not specify the second application.