x11: Use scoped_ptr<> for X11 objects where it makes sense.

ash/host/ash_window_tree_host_x11.cc

 // Copyright 2014 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 "ash/host/ash_window_tree_host_x11.h"
 
 #include <X11/extensions/Xfixes.h>
 #include <X11/extensions/XInput2.h>
 #include <X11/Xatom.h>
 #include <X11/Xlib.h>
@@ skipping 229 matching lines @@
   SendEventToProcessor(event);
 }
 
 #if defined(OS_CHROMEOS)
 void AshWindowTreeHostX11::SetCrOSTapPaused(bool state) {
   if (!ui::IsXInput2Available())
     return;
   // Temporarily pause tap-to-click when the cursor is hidden.
   Atom prop = atom_cache()->GetAtom("Tap Paused");
   unsigned char value = state;
-  XIDeviceList dev_list =
+  const XIDeviceList& dev_list =
       ui::DeviceListCacheX11::GetInstance()->GetXI2DeviceList(xdisplay());
 
   // Only slave pointer devices could possibly have tap-paused property.
   for (int i = 0; i < dev_list.count; i++) {
     if (dev_list[i].use == XISlavePointer) {
       Atom old_type;
       int old_format;
       unsigned long old_nvalues, bytes;
       unsigned char* data;
       int result = XIGetProperty(xdisplay(),
@@ skipping 23 matching lines @@
   }
 }
 #endif
 
 AshWindowTreeHost* AshWindowTreeHost::Create(
     const AshWindowTreeHostInitParams& init_params) {
   return new AshWindowTreeHostX11(init_params.initial_bounds);
 }
 
 }  // namespace ash