1. A method executed by one or more computing devices for securing execution of a web application in a non-native execution environment, the method comprising: executing, by at least one of the one or more computing devices, a function of the web application in the non-native execution environment, wherein the web application comprises only a portion of a plurality of execution dependencies required for execution of the web application and wherein the web application comprises one or more partial execution stub (PES) functions configured to bridge one or more missing execution dependencies in the plurality of execution dependencies; detecting, by at least one of the one or more computing devices, invocation of a PES function in the one or more PES functions during execution of the function of the web application, wherein the PES function corresponds to a missing execution dependency in the one or more missing execution dependencies; generating, by at least one of the one or more computing devices, a message comprising current execution information of the web application, the current execution information including an identifier of the PES function and an identifier of the function of the web application; transmitting, by at least one of the one or more computing devices, the message to a trusted module external to the non-native execution environment via a communication connection between the PES function and the trusted module, wherein the trusted module is configured to perform a search for the missing execution dependency based at least in part on the identifier of the PES function and the identifier of the function of the web application; and receiving, by at least one of the one or more computing devices, a result of the search from the trusted module via the communication connection between the PES function and the trusted module, wherein the result comprises an execution dependency corresponding to the missing execution dependency when the search is successful.