Implemented parseSingleValue in CSSPropertyAPICounterIncrement.

third_party/WebKit/Source/core/css/CSSProperties.json5

 {
 // This file specifies all the CSS properties we support and the necessary
 // information for our code generation. The various supported arguments
 // are described below with example usage
 
   parameters: {
     // - alias_for: "other-property"
     // Properties specifying alias_for should be virtually identical to the
     // properties they alias. Minor parsing differences are allowed as long as
     // the CSSValues created are of the same format of the aliased property.
@@ skipping 899 matching lines @@
       name: "content",
       api_class: true,
       api_methods: ["parseSingleValue"],
       custom_all: true,
       separator: ",",
       typedom_types: ["Image"],
     },
     {
       name: "counter-increment",
       api_class: true,
+      api_methods: ["parseSingleValue"],
       custom_all: true,
     },
     {
       name: "counter-reset",
       api_class: true,
       custom_all: true,
     },
     {
       name: "cursor",
       api_class: true,
@@ skipping 2253 matching lines @@
     {
       name: "-webkit-transition-timing-function",
       alias_for: "transition-timing-function",
     },
     {
       name: "-webkit-user-select",
       alias_for: "user-select",
     },
   ],
 }