src/vs/workbench/browser/parts/editor/editorPanes.ts/EditorPanes/doInstantiateEditorPane
class EditorPanes:	private doInstantiateEditorPane(descriptor: IEditorPaneDescriptor): EditorPane {

		// Return early if already instantiated
		const existingEditorPane = this.editorPanes.find(editorPane => descriptor.describes(editorPane));
		if (existingEditorPane) {
			return existingEditorPane;
		}

		// Otherwise instantiate new
		const editorPane = this._register(descriptor.instantiate(this.instantiationService));
		this.editorPanes.push(editorPane);

		return editorPane;
	}