1. One or more computer-readable storage media embodying computer-readable instructions which, when executed, implement a method comprising: building a display tree associated with a webpage that has been received; setting at least one flag on a display tree node of the display tree associated with the webpage corresponding to an element for which a default touch behavior has been specified using a declarative style; conducting an independent hit test on the display tree associated with the webpage; and calling a manipulation thread for direct manipulation of one or more elements for which a default touch behavior has been specified.