Source Map Generation corrupts property access with setUseOriginalNamesInOutput(true)

If you specify any sourceMapOutputPath together with `options.setUseOriginalNamesInOutput(true)`, then any property looses its object:

```javascript
String code = "console.log(document.readyState)";

final Compiler compiler = new Compiler();
final CompilerOptions options = new CompilerOptions();

options.setUseOriginalNamesInOutput(true);

// This option breaks the code:
options.setSourceMapOutputPath("/dev/null"); // any path

final SourceFile input = SourceFile.fromCode("js-input.js", code);
compiler.compile(Arrays.asList(), Arrays.asList(input), options);
final String compiled = compiler.toSource();

System.out.println(compiled); // should be "console.log(x.u);", but is "log(u);"
```