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

content/browser/web_contents/web_contents_impl.cc

Index: content/browser/web_contents/web_contents_impl.cc
diff --git a/content/browser/web_contents/web_contents_impl.cc b/content/browser/web_contents/web_contents_impl.cc
index 23a03d9b75fac5e2fd7bb91fa7001bfe8296fbcc..b25739fe858cb8b82756c8144e8e83a4191332be 100644
--- a/content/browser/web_contents/web_contents_impl.cc
+++ b/content/browser/web_contents/web_contents_impl.cc
@@ -970,6 +970,23 @@ void WebContentsImpl::UpdateZoomIfNecessary(const std::string& scheme,
   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());