src/vs/workbench/contrib/preferences/common/preferencesContribution.ts/PreferencesContribution/start
class PreferencesContribution:	private start(): void {

		this.textModelResolverService.registerTextModelContentProvider('vscode', {
			provideTextContent: (uri: URI): Promise<ITextModel | null> | null => {
				if (uri.scheme !== 'vscode') {
					return null;
				}
				if (uri.authority === 'schemas') {
					const schemaModel = this.getSchemaModel(uri);
					if (schemaModel) {
						return Promise.resolve(schemaModel);
					}
				}
				return Promise.resolve(this.preferencesService.resolveModel(uri));
			}
		});
	}