window.postMessage doesn't seem to work the first time it's injected

[spite]

At the end of the injected function, there's a call to

window.postMessage( { source: 'WebGLShaderEditor', method: 'init' }, '*');

which doesn't seem to work. That message would signal that the WebGLRenderingContext has been hooked, and that everything is ready to start getting events, so the UI should be visible, or at least a message that says "Waiting for programs to be created..."

That doesn't work, so now I'm using the first "addProgram" message to signal that there's activity.