In sa.js dumpheap is implemented as:

    registerCommand("dumpheap", "dumpheap [ file ]", "dumpHeap");

The 3rd argument is the implementation. In this case it is a java method in JSJavaScriptEngine.java, which does the following:

    public Object dumpHeap(Object[] args) {
        String fileName = "heap.bin";
        if (args.length > 0) {
            fileName = args[0].toString();
        }
        return new JMap().writeHeapHprofBin(fileName)? Boolean.TRUE: Boolean.FALSE;
    }

So this java code is easily moved to CommandProcessor.java