new () should have return type

[kainino0x]

Currently IDL interfaces with constructors will generate declare vars like:

declare var GPUOutOfMemoryError: {
  prototype: GPUOutOfMemoryError;
  new ();
};

However some compiler settings (such as the ones used in gpuweb/cts) will actually consider new () to return any instead of the apparent usual default GPUOutOfMemoryError (I'm not exactly sure why), causing linter errors. Would be best to write the return type explicitly I think.

declare var GPUOutOfMemoryError: {
  prototype: GPUOutOfMemoryError;
  new (): GPUOutOfMemoryError;
};