Make SafeBrowsingResourceThrottleFactory::RegisterFactory() not optional.

chrome/browser/renderer_host/safe_browsing_resource_throttle_factory.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 CHROME_BROWSER_RENDERER_HOST_SAFE_BROWSING_RESOURCE_THROTTLE_FACTORY_H_
 #define CHROME_BROWSER_RENDERER_HOST_SAFE_BROWSING_RESOURCE_THROTTLE_FACTORY_H_
 
 #include "base/basictypes.h"
 
 class SafeBrowsingService;
 
 namespace content {
 class ResourceContext;
 class ResourceThrottle;
 }
 
 namespace net {
 class URLRequest;
 }
 
-// Factory for creating a SafeBrowsingResourceThrottle. When FULL_SAFE_BROWSING
-// is enabled, creates a SafeBrowsingResourceThrottle. When MOBILE_SAFE_BROWSING
-// is enabled, the default implementation creates a null resource throttle,
-// therefore, a factory has to be registered before using this.
+// Factory for creating a SafeBrowsingResourceThrottle. If a factory is
+// registered, the factory's CreateResourceThrottle() is called.  Otherwise,
+// when FULL_SAFE_BROWSING is enabled, a new SafeBrowsingResourceThrottle is
+// returned, or NULL if MOBILE_SAFE_BROWSING is enabled.
 class SafeBrowsingResourceThrottleFactory {
  public:
-#if defined(FULL_SAFE_BROWSING) || defined(MOBILE_SAFE_BROWSING)
   // Registers a factory. Does not take the ownership of the factory. The
   // caller has to make sure the factory stays alive and properly destroyed.
-  static void RegisterFactory(SafeBrowsingResourceThrottleFactory* factory) {
-    factory_ = factory;
-  }
-#endif
+  static void RegisterFactory(SafeBrowsingResourceThrottleFactory* factory);
 
   // Creates a new resource throttle for safe browsing
   static content::ResourceThrottle* Create(
       net::URLRequest* request,
       content::ResourceContext* resource_context,
       bool is_subresource,
       SafeBrowsingService* service);
 
  protected:
   SafeBrowsingResourceThrottleFactory() { }
   virtual ~SafeBrowsingResourceThrottleFactory() { }
 
   virtual content::ResourceThrottle* CreateResourceThrottle(
       net::URLRequest* request,
       content::ResourceContext* resource_context,
       bool is_subresource,
       SafeBrowsingService* service) = 0;
 
  private:
   static SafeBrowsingResourceThrottleFactory* factory_;
 
   DISALLOW_COPY_AND_ASSIGN(SafeBrowsingResourceThrottleFactory);
 };
 
 #endif  // CHROME_BROWSER_RENDERER_HOST_SAFE_BROWSING_RESOURCE_THROTTLE_FACTORY_H_