Initial background according to theme, need to set backgroundColor window color

src/vs/code/electron-main/window.ts

@@ -180,8 +180,7 @@ export class VSCodeWindow {
 			height: this.windowState.height,
 			x: this.windowState.x,
 			y: this.windowState.y,
-			backgroundColor: '#00000000',
-			transparent: true,
+			backgroundColor: this.getBackgroundColor(),
 			minWidth: VSCodeWindow.MIN_WIDTH,
 			minHeight: VSCodeWindow.MIN_HEIGHT,
 			show: !isFullscreenOrMaximized,