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..3f52224c12841d038297962d67234826b93dce8a 100644
--- a/third_party/WebKit/Source/core/css/parser/CSSPropertyParserHelpers.h
+++ b/third_party/WebKit/Source/core/css/parser/CSSPropertyParserHelpers.h
@@ -11,6 +11,7 @@
 #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"
 
@@ -78,11 +79,14 @@ CSSValue* ConsumeColor(CSSParserTokenRange&,
 CSSValue* ConsumeLineWidth(CSSParserTokenRange&, CSSParserMode, UnitlessQuirk);
 
 CSSValuePair* ConsumePosition(CSSParserTokenRange&,
-                              CSSParserMode,
-                              UnitlessQuirk);
+                              const CSSParserContext&,
+                              UnitlessQuirk,
+                              UseCounter::Feature);
 bool ConsumePosition(CSSParserTokenRange&,
-                     CSSParserMode,
+                     const CSSParserContext&,
                      UnitlessQuirk,
+                     UseCounter::Feature,  // Pass kNumberOfFeatures if three
+                                           // value positions are not permitted.
                      CSSValue*& result_x,
                      CSSValue*& result_y);
 bool ConsumeOneOrTwoValuedPosition(CSSParserTokenRange&,