CompilerOptions options = new CompilerOptions();
options.sourceMapOutputPath = "";
Result result = compiler.compile(extern, input, options);
String compressedSrc = compiler.toSource();
StringBuffer sb = new StringBuffer();
Note in the code above the attached URL points to the Zazl HTTP handler to obtain the source map for a given module when the HTTP request contains a "sourcemap" parameter.
Update 9/27/2012 :
The good news is with these changes in place the Chrome debugger now shows and links to all source files correctly. The bad news is that doing other debug tasks, such as setting breakpoints, do not work.