* Electron version: 1.6.1
* Operating system: MacOS 10.12

Create a webview, set the zoom level, then create a second webview for content at the same domain as the 1st webview.

### Expected behavior

Ideally the second webview would assume the same zoom as the existing webview. At minumum, it'd be good if the first webview maintained its current zoom.

### Actual behavior

The zoom level is reset on both webviews.

### How to reproduce

https://github.com/pfrazee/electron-bug-webview-zoom Instructions on the readme
atom/browser/web_contents_zoom_controller.h
void SetTemporaryZoomLevel(double level);
  bool UsesTemporaryZoomLevel();
 protected:
  
  void DidFinishNavigation(content::NavigationHandle* handle) override;
  void WebContentsDestroyed() override;
  void RenderFrameHostChanged(content::RenderFrameHost* old_host,
                              content::RenderFrameHost* new_host) override;
 private:
  friend class content::WebContentsUserData<WebContentsZoomController>;
  
  void SetZoomFactorOnNavigationIfNeeded(const GURL& url);
  
  void OnZoomLevelChanged(const content::HostZoomMap::ZoomLevelChange& change);
  
  double default_zoom_factor_;
  double temporary_zoom_level_;
  int old_process_id_;
  int old_view_id_;
  WebContentsZoomController* embedder_zoom_controller_;
  
  std::map<std::string, double> host_zoom_factor_;
  base::ObserverList<Observer> observers_;
  content::HostZoomMap* host_zoom_map_;
  std::unique_ptr<content::HostZoomMap::Subscription> zoom_subscription_;
  DISALLOW_COPY_AND_ASSIGN(WebContentsZoomController);
};
}  
#endif