Fix missing shadows for modal window

ui/views/widget/desktop_aura/desktop_window_tree_host_x11.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/views/widget/desktop_aura/desktop_window_tree_host_x11.h"
 
 #include <X11/extensions/shape.h>
 #include <X11/extensions/XInput2.h>
 #include <X11/Xatom.h>
 #include <X11/Xregion.h>
@@ skipping 1341 matching lines @@
       window_type = atom_cache_.GetAtom("_NET_WM_WINDOW_TYPE_NORMAL");
       break;
   }
   // An in-activatable window should not interact with the system wm.
   if (!activatable_)
     swa.override_redirect = True;
 
   if (swa.override_redirect)
     attribute_mask |= CWOverrideRedirect;
 
+  Widget* widget = native_widget_delegate_->AsWidget();
   const bool enable_transparent_visuals =
       params.type == Widget::InitParams::TYPE_DRAG ||
-      params.type == Widget::InitParams::TYPE_WINDOW;
+      (params.type == Widget::InitParams::TYPE_WINDOW &&
+       params.wm_role_name == "browser") ||
+      (params.type == Widget::InitParams::TYPE_WINDOW && !widget->IsModal() &&
+       params.opacity == Widget::InitParams::TRANSLUCENT_WINDOW);
 
   Visual* visual = CopyFromParent;
   int depth = CopyFromParent;
   ui::ChooseVisualForWindow(enable_transparent_visuals, &visual, &depth);
   if (enable_transparent_visuals && depth == 32) {
     attribute_mask |= CWColormap;
     swa.colormap =
         XCreateColormap(xdisplay_, x_root_window_, visual, AllocNone);
 
     // x.org will BadMatch if we don't set a border when the depth isn't the
@@ skipping 938 matching lines @@
   if (linux_ui) {
     ui::NativeTheme* native_theme = linux_ui->GetNativeTheme(window);
     if (native_theme)
       return native_theme;
   }
 
   return ui::NativeThemeAura::instance();
 }
 
 }  // namespace views