Remove RenderWidget::SetBackground, change IPC to pass a bool.

apps/ui/views/native_app_window_views.cc

Index: apps/ui/views/native_app_window_views.cc
diff --git a/apps/ui/views/native_app_window_views.cc b/apps/ui/views/native_app_window_views.cc
index 22c384e43ac686b2ad7f95d7b5f8d2e2c9e1df33..7784cca8240319fdd7e0af7fa9dd34f23a23d1e5 100644
--- a/apps/ui/views/native_app_window_views.cc
+++ b/apps/ui/views/native_app_window_views.cc
@@ -262,15 +262,9 @@ void NativeAppWindowViews::OnWidgetActivationChanged(views::Widget* widget,
 void NativeAppWindowViews::RenderViewCreated(
     content::RenderViewHost* render_view_host) {
   if (transparent_background_) {
-    // Use a background with transparency to trigger transparency in Webkit.
-    SkBitmap background;
-    background.setConfig(SkBitmap::kARGB_8888_Config, 1, 1);
-    background.allocPixels();
-    background.eraseARGB(0x00, 0x00, 0x00, 0x00);
-
     content::RenderWidgetHostView* view = render_view_host->GetView();
     DCHECK(view);
-    view->SetBackground(background);
+    view->SetBackgroundOpaque(false);
   }
 }