[Linux] Show preview contents for minimized windows

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 1226 matching lines @@
             inserter(window_properties_, window_properties_.begin()));
 
   // Propagate the window minimization information to the content window, so
   // the render side can update its visibility properly. OnWMStateUpdated() is
   // called by PropertyNofify event from DispatchEvent() when the browser is
   // minimized or shown from minimized state. On Windows, this is realized by
   // calling OnHostResized() with an empty size. In particular,
   // HWNDMessageHandler::GetClientAreaBounds() returns an empty size when the
   // window is minimized. On Linux, returning empty size in GetBounds() or
   // SetBounds() does not work.
+  // We also propagate the minimization to the compositor, to makes sure that we
+  // don't draw any 'blank' frames that could be noticed in applications such as
+  // window manager previews, which show content even when a window is
+  // minimized.
   bool is_minimized = IsMinimized();
   if (is_minimized != was_minimized) {
-    if (is_minimized)
+    if (is_minimized) {
+      compositor()->SetVisible(false);
       content_window_->Hide();
-    else
+    } else {
       content_window_->Show();
+      compositor()->SetVisible(true);
+    }
   }
 
   if (restored_bounds_.IsEmpty()) {
     DCHECK(!IsFullscreen());
     if (IsMaximized()) {
       // The request that we become maximized originated from a different
       // process. |bounds_| already contains our maximized bounds. Do a best
       // effort attempt to get restored bounds by setting it to our previously
       // set bounds (and if we get this wrong, we aren't any worse off since
       // we'd otherwise be returning our maximized bounds).
@@ skipping 651 matching lines @@
   if (linux_ui) {
     ui::NativeTheme* native_theme = linux_ui->GetNativeTheme(window);
     if (native_theme)
       return native_theme;
   }
 
   return ui::NativeTheme::instance();
 }
 
 }  // namespace views