Remove unnecessary Document.h includes in .cpp files

Source/core/loader/BeaconLoader.cpp

 // 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.
 
 #include "config.h"
 #include "core/loader/BeaconLoader.h"
 
 #include "core/FetchInitiatorTypeNames.h"
-#include "core/dom/Document.h"
 #include "core/fetch/CrossOriginAccessControl.h"
 #include "core/fetch/FetchContext.h"
 #include "core/fileapi/File.h"
 #include "core/frame/LocalFrame.h"
 #include "core/html/DOMFormData.h"
 #include "platform/network/FormData.h"
 #include "platform/network/ParsedContentType.h"
 #include "platform/network/ResourceRequest.h"
 #include "wtf/ArrayBufferView.h"
 
@@ skipping 101 matching lines @@
     AtomicString contentType = AtomicString("multipart/form-data; boundary=", AtomicString::ConstructFromLiteral) + entityBody->boundary().data();
     request.setHTTPBody(entityBody.release());
     request.setHTTPContentType(contentType);
 
     issueRequest(frame, request);
     payloadLength = entitySize;
     return true;
 }
 
 } // namespace WebCore