1. A computer-implemented process for communicating executable scripts between iframe boundaries, comprising: using a computer to perform process actions for: instantiating a browser application hosting at least two iframes and loading separate scripts containing structured control flow of a scripting language into two or more of the iframes; automatically transforming at least a portion of the scripts within one or more of the iframes to cause the transformed scripts within those iframes to generate one or more annotated serialized text messages representing corresponding structured control flow when the transformed scripts initiate corresponding actions within those iframes; using a postMessage channel of the browser to transmit each annotated serialized text message from its corresponding iframe to one or more of the other iframes; and within any iframe receiving any annotated serialized text message from any other iframe, deserializing that message and converting it back into the corresponding structured control flow for execution within the receiving iframe.