Cross-process frames should be notified of device scale factor changes.

content/browser/web_contents/web_contents_impl.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 "content/browser/web_contents/web_contents_impl.h"
 
 #include <stddef.h>
 
 #include <cmath>
 #include <utility>
@@ skipping 952 matching lines @@
 
   GURL url = HostZoomMap::GetURLFromEntry(entry);
   if (host != net::GetHostOrSpecFromURL(url) ||
       (!scheme.empty() && !url.SchemeIs(scheme))) {
     return;
   }
 
   UpdateZoom(level);
 }
 
+void WebContentsImpl::UpdateDeviceScaleFactor(double device_scale_factor) {
+  SendPageMessage(
+      new PageMsg_SetDeviceScaleFactor(MSG_ROUTING_NONE, device_scale_factor));
+}
+
+double WebContentsImpl::DefaultDeviceScaleFactor() {
+  // TODO(wjmaclean): is it simpler to just remember the value from the last
+  // call to UpdateDeviceScaleFactor()? It's perhaps not the sort of state we
+  // expect WebContents to be hanging on to.
+  RenderWidgetHostViewBase* rwhv =
+      static_cast<RenderWidgetHostViewBase*>(GetRenderWidgetHostView());
+  if (rwhv)
+    return rwhv->current_device_scale_factor();
+
+  return RenderWidgetHostDelegate::DefaultDeviceScaleFactor();
+}
+
 WebUI* WebContentsImpl::CreateSubframeWebUI(const GURL& url,
                                             const std::string& frame_name) {
   DCHECK(!frame_name.empty());
   return CreateWebUI(url, frame_name);
 }
 
 WebUI* WebContentsImpl::GetWebUI() const {
   WebUI* commited_web_ui = GetCommittedWebUI();
   return commited_web_ui ? commited_web_ui
                          : GetRenderManager()->GetNavigatingWebUI();
@@ skipping 4178 matching lines @@
   for (RenderViewHost* render_view_host : render_view_host_set)
     render_view_host->OnWebkitPreferencesChanged();
 }
 
 void WebContentsImpl::SetJavaScriptDialogManagerForTesting(
     JavaScriptDialogManager* dialog_manager) {
   dialog_manager_ = dialog_manager;
 }
 
 }  // namespace content