src/vs/workbench/browser/parts/editor/textEditor.ts/AbstractTextEditor/updateReadonly
class AbstractTextEditor:	protected updateReadonly(input: EditorInput): void {
		const readOnly = input.hasCapability(EditorInputCapabilities.Readonly);

		this.updateEditorControlOptions({
			readOnly,
			enableDropIntoEditor: !readOnly
		});
	}