MacViews: Implement BridgedNativeWidget::OnDeviceScaleFactorChanged function.

ui/views/cocoa/bridged_native_widget.mm

 // 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.
 
 #import "ui/views/cocoa/bridged_native_widget.h"
 
 #import <objc/runtime.h>
 
 #include "base/logging.h"
 #import "base/mac/foundation_util.h"
@@ skipping 855 matching lines @@
   native_widget_mac_->GetWidget()->OnNativeWidgetPaint(context);
 }
 
 void BridgedNativeWidget::OnDelegatedFrameDamage(
     const gfx::Rect& damage_rect_in_dip) {
   NOTIMPLEMENTED();
 }
 
 void BridgedNativeWidget::OnDeviceScaleFactorChanged(
     float device_scale_factor) {
-  NOTIMPLEMENTED();
+  native_widget_mac_->GetWidget()->DeviceScaleFactorChanged(
+      device_scale_factor);
 }
 
 base::Closure BridgedNativeWidget::PrepareForLayerBoundsChange() {
   NOTIMPLEMENTED();
   return base::Closure();
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 // BridgedNativeWidget, AcceleratedWidgetMac:
 
@@ skipping 283 matching lines @@
   [bridged_view_ setMouseDownCanMoveWindow:draggable];
   // AppKit will not update its cache of mouseDownCanMoveWindow unless something
   // changes. Previously we tried adding an NSView and removing it, but for some
   // reason it required reposting the mouse-down event, and didn't always work.
   // Calling the below seems to be an effective solution.
   [window_ setMovableByWindowBackground:NO];
   [window_ setMovableByWindowBackground:YES];
 }
 
 }  // namespace views