ios: Cleanup class/struct forward declarations

ios/chrome/browser/physical_web/ios_chrome_physical_web_data_source.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 IOS_CHROME_BROWSER_PHYSICAL_WEB_IOS_CHROME_PHYSICAL_WEB_DATA_SOURCE_H_
 #define IOS_CHROME_BROWSER_PHYSICAL_WEB_IOS_CHROME_PHYSICAL_WEB_DATA_SOURCE_H_
 
 #include "base/macros.h"
 #import "base/mac/scoped_nsobject.h"
 #include "components/physical_web/data_source/physical_web_data_source_impl.h"
 
 namespace base {
 class ListValue;
 }
-class PhysicalWebListener;
 
 @class PhysicalWebScanner;
 
 // iOS implementation of PhysicalWebDataSource
 class IOSChromePhysicalWebDataSource
     : public physical_web::PhysicalWebDataSourceImpl {
  public:
   IOSChromePhysicalWebDataSource();
   ~IOSChromePhysicalWebDataSource() override;
 
@@ skipping 13 matching lines @@
   bool HasUnresolvedDiscoveries() override;
 
  private:
   // Scanner for nearby Physical Web URL devices.
   base::scoped_nsobject<PhysicalWebScanner> scanner_;
 
   DISALLOW_COPY_AND_ASSIGN(IOSChromePhysicalWebDataSource);
 };
 
 #endif  // IOS_CHROME_COMMON_PHYSICAL_WEB_IOS_CHROME_PHYSICAL_WEB_DATA_SOURCE_H_