We currently currently fire an error event for every module dependency that fails to load in a module graph. We should only fire a single event.

The first change is to make ScriptLoader::OnStreamComplete not fire an event for non-top-level modules. However now we have to make sure top-level modules also fire error events. Currently, inline script elements don't fire error events (because there can never be an error fetching an inline script). I was unsure of the best way to do this. What I've done here is to change the aIsInline parameter to ScriptElement::ScriptAvailable to aIsInlineClassicScript, because that is the test that we want to make. This works but it isn't great because it leaks into the nsIScriptLoaderObserver interface. Is this is OK or do you think there is there a better way to do this?

Pushed by jcoppeard@mozilla.com: https://hg.mozilla.org/integration/mozilla-inbound/rev/aaf6dde0deb8 Fix error events fired when loading JS module dependencies fail r=baku