Revert of Maintain HostZoom connection per-frame on browser side

content/browser/host_zoom_map_observer.h

 // Copyright 2016 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_OBSERVER_H_
 #define CONTENT_BROWSER_HOST_ZOOM_MAP_OBSERVER_H_
 
 #include "content/common/host_zoom.mojom.h"
 #include "content/public/browser/web_contents_observer.h"
 
 namespace content {
 
 class RenderFrameHost;
 
 class HostZoomMapObserver : private WebContentsObserver {
  public:
   explicit HostZoomMapObserver(WebContents* web_contents);
   ~HostZoomMapObserver() override;
 
  private:
   // WebContentsObserver implementation:
   void ReadyToCommitNavigation(NavigationHandle* navigation_handle) override;
   void RenderFrameCreated(RenderFrameHost* rfh) override;
-  void RenderFrameDeleted(RenderFrameHost* rfh) override;
 
-  std::map<RenderFrameHost*, mojom::HostZoomAssociatedPtr> host_zoom_ptrs_;
+  mojom::HostZoomAssociatedPtr host_zoom_;
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_HOST_ZOOM_MAP_OBSERVER_H_