The Sky parser should yield before start tags

sky/engine/core/html/parser/BackgroundHTMLParser.h

 /*
  * Copyright (C) 2013 Google, Inc. All Rights Reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 50 matching lines @@
     // DataPipeDrainer::Client:
     void OnDataAvailable(const void* data, size_t numberOfBytes) override;
     void OnDataComplete() override;
 
     void finish();
     void markEndOfFile();
     void pumpTokenizer();
     void sendTokensToMainThread();
     bool updateTokenizerState(const CompactHTMLToken& token);
 
+    enum State {
+        InitialState,
+        DidSeeImportState,
+    };
+
+    State m_state;
     SegmentedString m_input;
     OwnPtr<HTMLToken> m_token;
     OwnPtr<HTMLTokenizer> m_tokenizer;
     base::WeakPtr<HTMLDocumentParser> m_parser;
 
     OwnPtr<CompactHTMLTokenStream> m_pendingTokens;
     OwnPtr<TextResourceDecoder> m_decoder;
 
     mojo::ScopedDataPipeConsumerHandle m_source;
     OwnPtr<mojo::common::DataPipeDrainer> m_drainer;
 
     base::WeakPtrFactory<BackgroundHTMLParser> m_weakFactory;
 };
 
 }
 
 #endif  // SKY_ENGINE_CORE_HTML_PARSER_BACKGROUNDHTMLPARSER_H_