Fix "unused variable" warnings.

ash/wm/boot_splash_screen_chromeos.cc

 // Copyright 2013 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/wm/boot_splash_screen_chromeos.h"
 
 #include "third_party/skia/include/core/SkBitmap.h"
 #include "ui/aura/window.h"
 #include "ui/aura/window_tree_host.h"
 #include "ui/compositor/layer.h"
 #include "ui/compositor/layer_type.h"
 #include "ui/compositor/paint_recorder.h"
 #include "ui/compositor/scoped_layer_animation_settings.h"
 #include "ui/gfx/canvas.h"
 
 #if defined(USE_X11)
 #include "ui/base/x/x11_util.h"  // nogncheck
 #endif
 
 namespace ash {
 
 // ui::LayerDelegate that copies the aura host window's content to a ui::Layer.
 class BootSplashScreen::CopyHostContentLayerDelegate
     : public ui::LayerDelegate {
  public:
   explicit CopyHostContentLayerDelegate(aura::WindowTreeHost* host)
-      : host_(host) {
+#if defined(USE_X11)
+      : host_(host)
+#endif
+  {
   }
 
   ~CopyHostContentLayerDelegate() override {}
 
   // ui::LayerDelegate overrides:
   void OnPaintLayer(const ui::PaintContext& context) override {
     // It'd be safer to copy the area to a canvas in the constructor and then
     // copy from that canvas to this one here, but this appears to work (i.e. we
     // only call this before we draw our first frame) and it saves us an extra
     // copy.
@@ skipping 12 matching lines @@
 
   void OnDelegatedFrameDamage(const gfx::Rect& damage_rect_in_dip) override {}
 
   void OnDeviceScaleFactorChanged(float device_scale_factor) override {}
 
   base::Closure PrepareForLayerBoundsChange() override {
     return base::Closure();
   }
 
  private:
+#if defined(USE_X11)
   aura::WindowTreeHost* host_;  // not owned
+#endif
 
   DISALLOW_COPY_AND_ASSIGN(CopyHostContentLayerDelegate);
 };
 
 BootSplashScreen::BootSplashScreen(aura::WindowTreeHost* host)
     : layer_delegate_(new CopyHostContentLayerDelegate(host)),
       layer_(new ui::Layer(ui::LAYER_TEXTURED)) {
   layer_->set_delegate(layer_delegate_.get());
 
   ui::Layer* root_layer = host->window()->layer();
   layer_->SetBounds(gfx::Rect(host->window()->bounds().size()));
   root_layer->Add(layer_.get());
   root_layer->StackAtTop(layer_.get());
 }
 
 BootSplashScreen::~BootSplashScreen() {
 }
 
 void BootSplashScreen::StartHideAnimation(base::TimeDelta duration) {
   ui::ScopedLayerAnimationSettings settings(layer_->GetAnimator());
   settings.SetTransitionDuration(duration);
   settings.SetPreemptionStrategy(ui::LayerAnimator::REPLACE_QUEUED_ANIMATIONS);
   layer_->SetOpacity(0.0f);
 }
 
 }  // namespace ash