Remove RuntimeAPIDelegate::GetPreviousVersion.

chrome/browser/extensions/api/runtime/chrome_runtime_api_delegate.h

 // Copyright 2014 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 CHROME_BROWSER_EXTENSIONS_API_RUNTIME_CHROME_RUNTIME_API_DELEGATE_H_
 #define CHROME_BROWSER_EXTENSIONS_API_RUNTIME_CHROME_RUNTIME_API_DELEGATE_H_
 
 #include <map>
 #include <string>
 #include <utility>
@@ skipping 32 matching lines @@
 
   // Sets a custom TickClock to use in tests.
   static void set_tick_clock_for_tests(base::TickClock* clock);
 
  private:
   friend class extensions::RuntimeAPI;
 
   // extensions::RuntimeAPIDelegate implementation.
   void AddUpdateObserver(extensions::UpdateObserver* observer) override;
   void RemoveUpdateObserver(extensions::UpdateObserver* observer) override;
-  base::Version GetPreviousExtensionVersion(
-      const extensions::Extension* extension) override;
   void ReloadExtension(const std::string& extension_id) override;
   bool CheckForUpdates(const std::string& extension_id,
                        const UpdateCheckCallback& callback) override;
   void OpenURL(const GURL& uninstall_url) override;
   bool GetPlatformInfo(extensions::api::runtime::PlatformInfo* info) override;
   bool RestartDevice(std::string* error_message) override;
   bool OpenOptionsPage(const extensions::Extension* extension,
                        content::BrowserContext* browser_context) override;
 
   // content::NotificationObserver implementation.
@@ skipping 28 matching lines @@
   std::map<std::string, UpdateCheckInfo> update_check_info_;
 
   ScopedObserver<extensions::ExtensionRegistry,
                  extensions::ExtensionRegistryObserver>
       extension_registry_observer_;
 
   DISALLOW_COPY_AND_ASSIGN(ChromeRuntimeAPIDelegate);
 };
 
 #endif  // CHROME_BROWSER_EXTENSIONS_API_RUNTIME_CHROME_RUNTIME_API_DELEGATE_H_