Check if the parserthread has been shut down before returning it to the ThreadedDataProvider

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 9dd3684ca179f63005528bae1df2b5f8b21bf85c..f295cf2a99fd72516da16b5e253bfef5a63fcacd 100644
--- a/Source/core/html/parser/HTMLDocumentParser.cpp
+++ b/Source/core/html/parser/HTMLDocumentParser.cpp
@@ -85,14 +85,17 @@ public:
     // WebThreadedDataReceiver
     virtual void acceptData(const char* data, int dataLength) OVERRIDE FINAL
     {
-        ASSERT(backgroundThread()->isCurrentThread());
+        ASSERT(backgroundThread() && backgroundThread()->isCurrentThread());
         if (m_backgroundParser.get())
             m_backgroundParser.get()->appendRawBytesFromParserThread(data, dataLength);
     }
 
     virtual blink::WebThread* backgroundThread() OVERRIDE FINAL
     {
-        return &HTMLParserThread::shared()->platformThread();
+        if (HTMLParserThread::shared())
+            return &HTMLParserThread::shared()->platformThread();
+
+        return 0;
     }
 
 private: