src/vs/workbench/browser/parts/editor/editorDropTarget.ts/DropOverlay/toggleDropIntoPrompt
class DropOverlay:	private toggleDropIntoPrompt(showing: boolean) {
		if (!this.dropIntoPromptElement) {
			return;
		}
		this.dropIntoPromptElement.style.opacity = showing ? '1' : '0';
	}