Make it possible to modify background HTML parser token limits.

Source/core/html/parser/BackgroundHTMLParser.h

Index: Source/core/html/parser/BackgroundHTMLParser.h
diff --git a/Source/core/html/parser/BackgroundHTMLParser.h b/Source/core/html/parser/BackgroundHTMLParser.h
index d283adfc215fb4f3e4b9d15a9cd1b7461c6a519b..ebc1f9cce947441268ec97b55c6bfaaf1289e513 100644
--- a/Source/core/html/parser/BackgroundHTMLParser.h
+++ b/Source/core/html/parser/BackgroundHTMLParser.h
@@ -48,11 +48,16 @@ class BackgroundHTMLParser {
     WTF_MAKE_FAST_ALLOCATED(BackgroundHTMLParser);
 public:
     struct Configuration {
+        Configuration();
         HTMLParserOptions options;
         WeakPtr<HTMLDocumentParser> parser;
         OwnPtr<XSSAuditor> xssAuditor;
         OwnPtr<TokenPreloadScanner> preloadScanner;
         OwnPtr<TextResourceDecoder> decoder;
+        // outstandingTokenLimit must be greater than or equal to
+        // pendingTokenLimit
+        size_t outstandingTokenLimit;
+        size_t pendingTokenLimit;
     };
 
     static void start(PassRefPtr<WeakReference<BackgroundHTMLParser>>, PassOwnPtr<Configuration>, WebScheduler*);
@@ -96,9 +101,11 @@ private:
     OwnPtr<HTMLTokenizer> m_tokenizer;
     HTMLTreeBuilderSimulator m_treeBuilderSimulator;
     HTMLParserOptions m_options;
+    const size_t m_outstandingTokenLimit;
     WeakPtr<HTMLDocumentParser> m_parser;
 
     OwnPtr<CompactHTMLTokenStream> m_pendingTokens;
+    const size_t m_pendingTokenLimit;
     PreloadRequestStream m_pendingPreloads;
     XSSInfoStream m_pendingXSSInfos;