Add setting to isolate zoom changes by default.

content/browser/host_zoom_map_impl.h

 // 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.
 
 #ifndef CONTENT_BROWSER_HOST_ZOOM_MAP_IMPL_H_
 #define CONTENT_BROWSER_HOST_ZOOM_MAP_IMPL_H_
 
 #include <map>
 #include <string>
 #include <tuple>
@@ skipping 18 matching lines @@
  public:
   HostZoomMapImpl();
   ~HostZoomMapImpl() override;
 
   // HostZoomMap implementation:
   void SetPageScaleFactorIsOneForView(
       int render_process_id, int render_view_id, bool is_one) override;
   void ClearPageScaleFactorIsOneForView(
       int render_process_id, int render_view_id) override;
   void CopyFrom(HostZoomMap* copy) override;
+  void PreserveTemporaryZoomLevelFrom(
+      const HostZoomMap* copy, RenderFrameHost* old_host,
+      RenderFrameHost* new_host) override;
   double GetZoomLevelForHostAndScheme(const std::string& scheme,
                                       const std::string& host) const override;
   // TODO(wjmaclean) Should we use a GURL here? crbug.com/384486
   bool HasZoomLevel(const std::string& scheme,
                     const std::string& host) const override;
   ZoomLevelVector GetAllZoomLevels() const override;
   void SetZoomLevelForHost(const std::string& host, double level) override;
   void SetZoomLevelForHostAndScheme(const std::string& scheme,
                                     const std::string& host,
                                     double level) override;
@@ skipping 25 matching lines @@
                                   double level);
 
   // Sets the zoom level for the specified view. The level may be set for only
   // this view, or for the host, depending on UsesTemporaryZoomLevel().
   void SetZoomLevelForView(int render_process_id,
                            int render_view_id,
                            double level,
                            const std::string& host);
 
   // Returns the temporary zoom level that's only valid for the lifetime of
-  // the given WebContents (i.e. isn't saved and doesn't affect other
-  // WebContentses) if it exists, the default zoom level otherwise.
+  // the given view (i.e. isn't saved and doesn't affect other WebContentses)
+  // if it exists, the default zoom level otherwise.
   //
   // This may be called on any thread.
   double GetTemporaryZoomLevel(int render_process_id,
                                int render_view_id) const;
 
   // Returns the zoom level regardless of whether it's temporary, host-keyed or
   // scheme+host-keyed.
   //
   // This may be called on any thread.
   double GetZoomLevelForView(const GURL& url,
@@ skipping 61 matching lines @@
   mutable base::Lock lock_;
 
   NotificationRegistrar registrar_;
 
   DISALLOW_COPY_AND_ASSIGN(HostZoomMapImpl);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_HOST_ZOOM_MAP_IMPL_H_