Add HTML parser UMA for rewinds and chunk queue statistics.

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

 // Copyright 2015 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.
 
 #ifndef ParsedChunkQueue_h
 #define ParsedChunkQueue_h
 
 #include "core/html/parser/HTMLDocumentParser.h"
 #include "wtf/Deque.h"
 #include "wtf/OwnPtr.h"
@@ skipping 19 matching lines @@
     {
         return adoptRef(new ParsedChunkQueue);
     }
 
     ~ParsedChunkQueue();
 
     bool enqueue(PassOwnPtr<HTMLDocumentParser::ParsedChunk>);
     void clear();
 
     void takeAll(Vector<OwnPtr<HTMLDocumentParser::ParsedChunk>>&);
+    size_t peakPendingChunkCount();
+    size_t peakPendingTokenCount();
 
 private:
     ParsedChunkQueue();
 
     Mutex m_mutex;
     Vector<OwnPtr<HTMLDocumentParser::ParsedChunk>> m_pendingChunks;
+    size_t m_peakPendingChunkCount = 0;
+    size_t m_peakPendingTokenCount = 0;
+    size_t m_pendingTokenCount = 0;
 };
 
 } // namespace blink
 
 #endif