src/vs/workbench/common/editor/textEditorModel.ts/BaseTextEditorModel/setMode
class BaseTextEditorModel:	setMode(mode: string): void {
		if (!this.isResolved()) {
			return;
		}

		if (!mode || mode === this.textEditorModel.getModeId()) {
			return;
		}

		this.modelService.setMode(this.textEditorModel, this.modeService.create(mode));
	}