CSS: Use count position values with 3 parts

third_party/WebKit/Source/core/css/parser/CSSPropertyParserHelpers.h

Index: third_party/WebKit/Source/core/css/parser/CSSPropertyParserHelpers.h
diff --git a/third_party/WebKit/Source/core/css/parser/CSSPropertyParserHelpers.h b/third_party/WebKit/Source/core/css/parser/CSSPropertyParserHelpers.h
index e1f2a5f6a246ddc69af242a03f058341d0602292..7c3259b9aa9766c434ab0c54a508681a36f5d7b6 100644
--- a/third_party/WebKit/Source/core/css/parser/CSSPropertyParserHelpers.h
+++ b/third_party/WebKit/Source/core/css/parser/CSSPropertyParserHelpers.h
@@ -11,8 +11,10 @@
 #include "core/css/CSSValueList.h"
 #include "core/css/parser/CSSParserMode.h"
 #include "core/css/parser/CSSParserTokenRange.h"
+#include "core/frame/UseCounter.h"
 #include "platform/Length.h"  // For ValueRange
 #include "platform/heap/Handle.h"
+#include "platform/wtf/Optional.h"
 
 namespace blink {
 
@@ -77,12 +79,15 @@ CSSValue* ConsumeColor(CSSParserTokenRange&,
 
 CSSValue* ConsumeLineWidth(CSSParserTokenRange&, CSSParserMode, UnitlessQuirk);
 
-CSSValuePair* ConsumePosition(CSSParserTokenRange&,
-                              CSSParserMode,
-                              UnitlessQuirk);
+CSSValuePair* ConsumePosition(
+    CSSParserTokenRange&,
+    const CSSParserContext&,
+    UnitlessQuirk,
+    WTF::Optional<UseCounter::Feature> threeValuePosition);
 bool ConsumePosition(CSSParserTokenRange&,
-                     CSSParserMode,
+                     const CSSParserContext&,
                      UnitlessQuirk,
+                     WTF::Optional<UseCounter::Feature> threeValuePosition,
                      CSSValue*& result_x,
                      CSSValue*& result_y);
 bool ConsumeOneOrTwoValuedPosition(CSSParserTokenRange&,