Make WebVTTParser::collectTimeStamp static

Source/core/html/track/WebVTTParser.h

Index: Source/core/html/track/WebVTTParser.h
diff --git a/Source/core/html/track/WebVTTParser.h b/Source/core/html/track/WebVTTParser.h
index 60e098e0eeded7e4fc093d0c38f41966d290e89c..000b0119a9f37dd38efdd73a94fc9252af8fd47c 100644
--- a/Source/core/html/track/WebVTTParser.h
+++ b/Source/core/html/track/WebVTTParser.h
@@ -93,6 +93,7 @@ public:
     }
     static String collectDigits(const String&, unsigned*);
     static String collectWord(const String&, unsigned*);
+    static double collectTimeStamp(const String&, unsigned*);
 
     // Useful functions for parsing percentage settings.
     static float parseFloatPercentageValue(const String&, bool&);
@@ -106,7 +107,6 @@ public:
     void getNewRegions(Vector<RefPtr<TextTrackRegion> >&);
 
     PassRefPtr<DocumentFragment> createDocumentFragmentFromCueText(const String&);
-    double collectTimeStamp(const String&, unsigned*);
 
 private:
     WebVTTParser(WebVTTParserClient*, Document&);