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 3c9c9a7cbc560e5c1165dfd469361766485b54aa..0c01f4a8e0c149f373141441c35bf478f847b9a8 100644
--- a/third_party/WebKit/Source/core/html/parser/ParsedChunkQueue.h
+++ b/third_party/WebKit/Source/core/html/parser/ParsedChunkQueue.h
@@ -37,12 +37,17 @@ public:
     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