JavaScript Heap Profiler can generate too much data

Profiling the QML Profiler in an old QtCreators painting the timeline overview for some seconds gives me a 1.3G trace file with almost only memory allocation events. It also takes forever to transfer the data. We need a way to limit this, at least optionally.

Maybe we should just stop collecting events after a certain threshold has been surpassed; the threshold could be configured with an additional command line parameter.