The initialisation of the browser windows seems to conflict with some of the changes at #577

Specifically, the windows are not composited for a couple seconds after they have been created, which triggers this code:

    if (mCompositionLayerColorScaleBias != XR_NULL_HANDLE) {
        vrb::Color tintColor = layer->GetTintColor();
        if (!IsComposited() && (layer->GetClearColor().Alpha() > 0.0f)) {
            tintColor = layer->GetClearColor();
            tintColor.SetRGBA(tintColor.Red(), tintColor.Green(), tintColor.Blue(), tintColor.Alpha());
        }
        mCompositionLayerColorScaleBiasStruct.colorScale = {tintColor.Red(), tintColor.Green(), tintColor.Blue(), tintColor.Alpha()};
    }

Upon creation, the window layer has these attributes:

• composited is false
• clearColor is set to our desired color, for example rgba(0.14,0.14,0.15,1.00)
• tint is set to white (rgba(1.00,1.00,1.00,1.00)) so the content is not modified

But with this code, colorScale becomes the same as the clearColor:

• colorScale is rgba(0.14,0.14,0.15,1.00)

What this means is that the clear color is being multiplied by itself, which will make it look different than expected.

Another useful change would be to allow us to set the background color for a website, similar to GeckoView.coverUntilFirstPaint.

Edit: implemented in PR #1827

Partial fix for #1766