Plumb resize notifications around sky/shell

sky/shell/ui/engine.cc

 // Copyright 2015 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 "sky/shell/ui/engine.h"
 
 #include "sky/engine/public/web/Sky.h"
 #include "sky/engine/public/web/WebLocalFrame.h"
 #include "sky/engine/public/web/WebView.h"
 #include "sky/shell/ui/platform_impl.h"
@@ skipping 14 matching lines @@
 }
 
 void Engine::Init() {
   platform_impl_.reset(new PlatformImpl);
   blink::initialize(platform_impl_.get());
 
   web_view_ = blink::WebView::create(this);
   web_view_->setMainFrame(blink::WebLocalFrame::create(this));
 }
 
+void Engine::OnViewportMetricsChanged(const gfx::Size& size,
+                                      float device_pixel_ratio) {
+  blink::WebSize web_size(size.width() / device_pixel_ratio,
+                          size.height() / device_pixel_ratio);
+  web_view_->setDeviceScaleFactor(device_pixel_ratio);
+  web_view_->resize(web_size);
+}
+
 }  // namespace shell
 }  // namespace sky