src/vs/workbench/api/browser/mainThreadDocumentsAndEditors.ts/MainThreadDocumentAndEditorStateComputer/_onDidAddEditor
class MainThreadDocumentAndEditorStateComputer:	private _onDidAddEditor(e: ICodeEditor): void {
		this._toDisposeOnEditorRemove.set(e.getId(), combinedDisposable(
			e.onDidChangeModel(() => this._updateState()),
			e.onDidFocusEditorText(() => this._updateState()),
			e.onDidFocusEditorWidget(() => this._updateState(e))
		));
		this._updateState();
	}