src/vs/workbench/browser/parts/editor/sideBySideEditor.ts/SideBySideEditor/updateStyles
class SideBySideEditor:	override updateStyles(): void {
		super.updateStyles();

		if (this.primaryEditorContainer) {
			this.primaryEditorContainer.style.boxShadow = `-6px 0 5px -5px ${this.getColor(scrollbarShadow)}`;
		}
	}