src/vs/editor/browser/widget/codeEditorWidget.ts/EditorContextKeysManager/_updateFromSelection
class EditorContextKeysManager:	private _updateFromSelection(): void {
		const selections = this._editor.getSelections();
		if (!selections) {
			this._hasMultipleSelections.reset();
			this._hasNonEmptySelection.reset();
		} else {
			this._hasMultipleSelections.set(selections.length > 1);
			this._hasNonEmptySelection.set(selections.some(s => !s.isEmpty()));
		}
	}