Add ZoomController to manager zoom changes for webcontents

atom/browser/web_contents_zoom_controller.h

@@ -0,0 +1,73 @@
+// Copyright (c) 2017 GitHub, Inc.
+// Use of this source code is governed by the MIT license that can be
+// found in the LICENSE file.
+
+#ifndef ATOM_BROWSER_WEB_CONTENTS_ZOOM_CONTROLLER_H_
+#define ATOM_BROWSER_WEB_CONTENTS_ZOOM_CONTROLLER_H_
+
+#include "content/public/browser/host_zoom_map.h"
+#include "content/public/browser/web_contents_observer.h"
+#include "content/public/browser/web_contents_user_data.h"
+
+namespace atom {
+
+// Manages the zoom changes of WebContents.
+class WebContentsZoomController
+    : public content::WebContentsObserver,
+      public content::WebContentsUserData<WebContentsZoomController> {
+ public:
+  class Observer {
+   public:
+    virtual void OnZoomLevelChanged(content::WebContents* web_contents,
+                                    double level) {}
+
+   protected:
+    virtual ~Observer() {}
+  };
+
+  explicit WebContentsZoomController(content::WebContents* web_contents);
+  ~WebContentsZoomController() override;
+
+  void AddObserver(Observer* observer);
+  void RemoveObserver(Observer* observer);
+
+  // Methods for managing zoom levels.
+  void SetZoomLevel(double level);
+  double GetZoomLevel();
+  void SetDefaultZoomFactor(double factor);
+  double GetDefaultZoomFactor();
+
+ protected:
+  // content::WebContentsObserver:
+  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>;
+
+  // Called after a navigation has committed to set default zoom factor.
+  void SetZoomFactorOnNavigationIfNeeded(const GURL& url);
+
+  // Track zoom changes of a host in other instances of a partition.
+  void OnZoomLevelChanged(const content::HostZoomMap::ZoomLevelChange& change);
+
+  // kZoomFactor.
+  double default_zoom_factor_;
+
+  // Map between zoom factor and hosts in this webContent.
+  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);
+};
+
+}  // namespace atom
+
+#endif  // ATOM_BROWSER_WEB_CONTENTS_ZOOM_CONTROLLER_H_