Remove willRequestResource callback, it is unused outside of tests.

Source/core/fetch/FetchContext.cpp

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 76 matching lines @@
 }
 
 void FetchContext::dispatchDidFail(unsigned long, const ResourceError&, bool)
 {
 }
 
 void FetchContext::sendRemainingDelegateMessages(unsigned long, const ResourceResponse&, int)
 {
 }
 
-void FetchContext::dispatchWillRequestResource(FetchRequest*)
-{
-}
-
 void FetchContext::willStartLoadingResource(ResourceRequest&)
 {
 }
 
 void FetchContext::didLoadResource()
 {
 }
 
 void FetchContext::addResourceTiming(const ResourceTimingInfo&)
 {
@@ skipping 13 matching lines @@
 
 void FetchContext::addClientHintsIfNecessary(FetchRequest&)
 {
 }
 
 void FetchContext::addCSPHeaderIfNecessary(Resource::Type, FetchRequest&)
 {
 }
 
 } // namespace blink