Reland of After detach, there's no document to notify parsing is finished.

third_party/WebKit/Source/core/html/parser/HTMLViewSourceParser.h

 /*
  * Copyright (C) 2010 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:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
  *
  * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
  * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #ifndef HTMLViewSourceParser_h
 #define HTMLViewSourceParser_h
 
+#include "core/CoreExport.h"
 #include "core/dom/DecodedDataDocumentParser.h"
 #include "core/html/HTMLViewSourceDocument.h"
 #include "core/html/parser/HTMLInputStream.h"
 #include "core/html/parser/HTMLSourceTracker.h"
 #include "core/html/parser/HTMLTokenizer.h"
 #include "core/html/parser/XSSAuditor.h"
 #include <memory>
 
 namespace blink {
 
-class HTMLViewSourceParser final : public DecodedDataDocumentParser {
+class CORE_EXPORT HTMLViewSourceParser final
+    : public DecodedDataDocumentParser {
  public:
   static HTMLViewSourceParser* create(HTMLViewSourceDocument& document,
                                       const String& mimeType) {
     return new HTMLViewSourceParser(document, mimeType);
   }
   ~HTMLViewSourceParser() override {}
 
  private:
   HTMLViewSourceParser(HTMLViewSourceDocument&, const String& mimeType);
 
@@ skipping 13 matching lines @@
   HTMLInputStream m_input;
   HTMLToken m_token;
   HTMLSourceTracker m_sourceTracker;
   std::unique_ptr<HTMLTokenizer> m_tokenizer;
   XSSAuditor m_xssAuditor;
 };
 
 }  // namespace blink
 
 #endif