Make DesktopWindowTreeHostX11::ShouldWindowContentsBeTransparent() relies on argb visual flag

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 766 matching lines @@
 void DesktopWindowTreeHostX11::SetVisibilityChangedAnimationsEnabled(
     bool value) {
   // Much like the previous NativeWidgetGtk, we don't have anything to do here.
 }
 
 bool DesktopWindowTreeHostX11::ShouldUseNativeFrame() const {
   return use_native_frame_;
 }
 
 bool DesktopWindowTreeHostX11::ShouldWindowContentsBeTransparent() const {
-  return false;
+  return IsTranslucentWindowOpacitySupported();
 }
 
 void DesktopWindowTreeHostX11::FrameTypeChanged() {
   Widget::FrameType new_type =
       native_widget_delegate_->AsWidget()->frame_type();
   if (new_type == Widget::FRAME_TYPE_DEFAULT) {
     // The default is determined by Widget::InitParams::remove_standard_frame
     // and does not change.
     return;
   }
@@ skipping 135 matching lines @@
 }
 
 void DesktopWindowTreeHostX11::OnNativeWidgetBlur() {
 }
 
 bool DesktopWindowTreeHostX11::IsAnimatingClosed() const {
   return false;
 }
 
 bool DesktopWindowTreeHostX11::IsTranslucentWindowOpacitySupported() const {
-  return false;
+  return use_argb_visual_;
 }
 
 void DesktopWindowTreeHostX11::SizeConstraintsChanged() {
   UpdateMinAndMaxSize();
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 // DesktopWindowTreeHostX11, aura::WindowTreeHost implementation:
 
 gfx::Transform DesktopWindowTreeHostX11::GetRootTransform() const {
@@ skipping 187 matching lines @@
   if (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
     // same as the parent depth.
     attribute_mask |= CWBorderPixel;
     swa.border_pixel = 0;
 
-    use_argb_visual_ = true;
+    // A compositing manager is required to support transparency.
+    XAtom NET_WM_CM_S0 = XInternAtom(xdisplay_, "_NET_WM_CM_S0", False);

[sadrul, 2016/06/24 03:55:13]

Use atom_cache_.GetAtom("_NET_WM_CM_S0") instead

[Julien Isorce Samsung, 2016/06/24 05:25:19]

Done.

+    use_argb_visual_ = XGetSelectionOwner(xdisplay_, NET_WM_CM_S0) != None;
   }
 
   bounds_in_pixels_ = ToPixelRect(params.bounds);
   bounds_in_pixels_.set_size(AdjustSize(bounds_in_pixels_.size()));
   xwindow_ = XCreateWindow(xdisplay_, x_root_window_, bounds_in_pixels_.x(),
                            bounds_in_pixels_.y(), bounds_in_pixels_.width(),
                            bounds_in_pixels_.height(),
                            0,  // border width
                            depth, InputOutput, visual, attribute_mask, &swa);
   if (ui::PlatformEventSource::GetInstance())
@@ skipping 905 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