Systems and methods for locally managing a user's interaction with content derived from web pages within the user interface of an application executing within a runtime provided by an application platform on a computing device in accordance with embodiments of the invention are disclosed. In many embodiments, a runtime provided by an application platform enables the execution of a non-natively implemented hosted application in which executing instructions in a scripting language within a background page control the downloading and modification of web content to create user interface pages for the hosted application.