Revert "cros: Allow frame-less windows to show shadow"

This reverts commit 40b9105e.

Reason for revert: affecting virtual keyboard UI in google3 (crbug.com/877302)

Original change's description:
> cros: Allow frame-less windows to show shadow
> 
> The current code assumes that a frame-less window does not need shadow.
> However, it's important for the CrOS wallpaper picker to remain
> frame-less to support wallpaper preview in tablet mode (spec [1]), and
> have a shadow in clamshell mode. It should makes sense to delete this
> logic since wallpaper picker is the only component extension that needs
> this behavior, and no current public apps are able to use the API.
> 
> [1] https://drive.google.com/corp/drive/folders/0B_2Uyb2Rhx2ObU5VTFJVWHR2WW8
> 
> Bug: 835205
> Change-Id: I96c9b14806f8f03ea2278d11031a33b08e7a68e8
> Reviewed-on: https://chromium-review.googlesource.com/1135577
> Commit-Queue: Wenzhao (Colin) Zang <wzang@chromium.org>
> Reviewed-by: Ben Wells <benwells@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#582036}

TBR=tapted@chromium.org,benwells@chromium.org,wzang@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 835205
Change-Id: I4a840224924d691fd7545a8b6252368fe06161d7
Reviewed-on: https://chromium-review.googlesource.com/1187784Reviewed-by: Wenzhao (Colin) Zang <wzang@chromium.org>
Commit-Queue: Wenzhao (Colin) Zang <wzang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#585739}

chrome/browser/ui/views/apps/chrome_native_app_window_views.cc

@@ -111,9 +111,16 @@ void ChromeNativeAppWindowViews::InitializeDefaultWindow(
   init_params.delegate = this;
   init_params.remove_standard_frame = ShouldRemoveStandardFrame();
   init_params.use_system_default_icon = true;
-  if (create_params.alpha_enabled)
+  if (create_params.alpha_enabled) {
     init_params.opacity = views::Widget::InitParams::TRANSLUCENT_WINDOW;
 
+    // The given window is most likely not rectangular since it uses
+    // transparency and has no standard frame, don't show a shadow for it.
+    // TODO(skuhne): If we run into an application which should have a shadow
+    // but does not have, a new attribute has to be added.
+    if (IsFrameless())
+      init_params.shadow_type = views::Widget::InitParams::SHADOW_TYPE_NONE;
+  }
   init_params.keep_on_top = create_params.always_on_top;
   init_params.visible_on_all_workspaces =
       create_params.visible_on_all_workspaces;