The HTML parser should ignore incoming bytes when stopped, not just when detached.

Source/core/html/parser/HTMLDocumentParser.cpp

Index: Source/core/html/parser/HTMLDocumentParser.cpp
diff --git a/Source/core/html/parser/HTMLDocumentParser.cpp b/Source/core/html/parser/HTMLDocumentParser.cpp
index ff73092b2cbfbcead0f72a109aa85434652e03d4..84c9197c309a3f36d5ee241d57a959ea31b771b2 100644
--- a/Source/core/html/parser/HTMLDocumentParser.cpp
+++ b/Source/core/html/parser/HTMLDocumentParser.cpp
@@ -659,6 +659,7 @@ void HTMLDocumentParser::insert(const SegmentedString& source)
 
 void HTMLDocumentParser::startBackgroundParser()
 {
+    ASSERT(!isStopped());
     ASSERT(shouldUseThreading());
     ASSERT(!m_haveBackgroundParser);
     m_haveBackgroundParser = true;
@@ -964,7 +965,7 @@ void HTMLDocumentParser::resumeScheduledTasks()
 
 void HTMLDocumentParser::appendBytes(const char* data, size_t length)
 {
-    if (!length || isDetached())
+    if (!length || isStopped())
         return;
 
     if (shouldUseThreading()) {
@@ -996,6 +997,7 @@ void HTMLDocumentParser::flush()
 
 void HTMLDocumentParser::setDecoder(PassOwnPtr<TextResourceDecoder> decoder)
 {
+    ASSERT(decoder);
     DecodedDataDocumentParser::setDecoder(decoder);
 
     if (m_haveBackgroundParser)