1. A method for executing an application, comprising: executing the application in a web browser on a host system, wherein the application executes using a separate operating system process from an operating system process that executes the web browser on the host system; receiving an execution environment change notification for the application; and in response to the execution environment change notification, transitioning the application to execute in a second execution environment that operates independently of the web browser without interrupting execution of the application; wherein the method is performed by one or more computing devices.