Remove threading primitives from ParseHTMLOnMainThread

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

Index: third_party/WebKit/Source/core/html/parser/ParsedChunkQueue.h
diff --git a/third_party/WebKit/Source/core/html/parser/ParsedChunkQueue.h b/third_party/WebKit/Source/core/html/parser/ParsedChunkQueue.h
index b28e324bed4a1a07b416b2ce95dcec5464f55fc7..bfa964b1ddc741938f37ec51684e7df6e3ba02b3 100644
--- a/third_party/WebKit/Source/core/html/parser/ParsedChunkQueue.h
+++ b/third_party/WebKit/Source/core/html/parser/ParsedChunkQueue.h
@@ -42,7 +42,7 @@ public:
 private:
     ParsedChunkQueue();
 
-    Mutex m_mutex;
+    std::unique_ptr<Mutex> m_mutex;
     Vector<std::unique_ptr<HTMLDocumentParser::ParsedChunk>> m_pendingChunks;
     size_t m_peakPendingChunkCount = 0;
     size_t m_peakPendingTokenCount = 0;