src/vs/editor/standalone/browser/standaloneThemeService.ts/StandaloneThemeService/setTheme
class StandaloneThemeService:	public setTheme(themeName: string): void {
		let theme: StandaloneTheme | undefined;
		if (this._knownThemes.has(themeName)) {
			theme = this._knownThemes.get(themeName);
		} else {
			theme = this._knownThemes.get(VS_LIGHT_THEME_NAME);
		}
		this._updateActualTheme(theme);
	}