Add -XjsInteropMode option to SuperDevMode

The option is already present when compiling a GWT app and is required
to use JsInterop features like @JsType annotations. This change makes it
possible to debug the use of JsInterop features while in SuperDevMode.

Change-Id: I108754c59d34f4df6b3bd38df4109af2758f2ebe
2 files changed