Add HTML parser UMA for rewinds and chunk queue statistics.

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 d65f2924be772dd3135915f50aa2c45a794ba5a6..b28e324bed4a1a07b416b2ce95dcec5464f55fc7 100644
--- a/third_party/WebKit/Source/core/html/parser/ParsedChunkQueue.h
+++ b/third_party/WebKit/Source/core/html/parser/ParsedChunkQueue.h
@@ -36,12 +36,17 @@ public:
     void clear();
 
     void takeAll(Vector<std::unique_ptr<HTMLDocumentParser::ParsedChunk>>&);
+    size_t peakPendingChunkCount();
+    size_t peakPendingTokenCount();
 
 private:
     ParsedChunkQueue();
 
     Mutex m_mutex;
     Vector<std::unique_ptr<HTMLDocumentParser::ParsedChunk>> m_pendingChunks;
+    size_t m_peakPendingChunkCount = 0;
+    size_t m_peakPendingTokenCount = 0;
+    size_t m_pendingTokenCount = 0;
 };
 
 } // namespace blink