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..87d1890a3ac57a7c8ea59891cc64b7afda4c6412 100644
--- a/third_party/WebKit/Source/core/css/parser/CSSPropertyParserHelpers.h
+++ b/third_party/WebKit/Source/core/css/parser/CSSPropertyParserHelpers.h
@@ -37,6 +37,12 @@ CSSParserTokenRange ConsumeFunction(CSSParserTokenRange&);
 
 enum class UnitlessQuirk { kAllow, kForbid };
 
+enum class PositionSyntax {
+  kRejectThreeValues,
+  kPermitThreeValues,
+  kCountThreeValues

[Bugs Nash, 2017/05/22 04:36:10]

the purpose of this enum is unclear to me, it seems to be confounded as both an
input of whether 3 values are allowed, and an output of whether 3 values were
read. if that's the case a comment to that effect would be useful.

[Eric Willigers, 2017/05/22 06:08:35]

Changed to new approach where the use counter feature is passed in.

I've changed the scroll snap points properties to reject 3 value positions.
This is consistent with the spec, and has no compatibility impact as these
properties have not shipped.

+};
+
 CSSPrimitiveValue* ConsumeInteger(
     CSSParserTokenRange&,
     double minimum_value = -std::numeric_limits<double>::max());
@@ -78,11 +84,13 @@ CSSValue* ConsumeColor(CSSParserTokenRange&,
 CSSValue* ConsumeLineWidth(CSSParserTokenRange&, CSSParserMode, UnitlessQuirk);
 
 CSSValuePair* ConsumePosition(CSSParserTokenRange&,
-                              CSSParserMode,
-                              UnitlessQuirk);
+                              const CSSParserContext&,
+                              UnitlessQuirk,
+                              PositionSyntax&);
 bool ConsumePosition(CSSParserTokenRange&,
-                     CSSParserMode,
+                     const CSSParserContext&,
                      UnitlessQuirk,
+                     PositionSyntax&,
                      CSSValue*& result_x,
                      CSSValue*& result_y);
 bool ConsumeOneOrTwoValuedPosition(CSSParserTokenRange&,