Hi there,
The optimizations closure-compiler does require it to see your entire application,
so at the moment we do not have any kind of incremental compile option.
However, for your edit-compile-test cycle, you could use the SIMPLE optimizations which are much less expensive to execute.
We have a WHITESPACE_ONLY mode, but that name is misleading if you're asking the compiler to output a different language level than the input,
so I don't really recommend using it.
I hope that helps you out,
Bradford