Add CSS Transition support to registered custom properties

third_party/WebKit/Source/core/css/CSSPropertyEquality.cpp

Index: third_party/WebKit/Source/core/css/CSSPropertyEquality.cpp
diff --git a/third_party/WebKit/Source/core/css/CSSPropertyEquality.cpp b/third_party/WebKit/Source/core/css/CSSPropertyEquality.cpp
index 8c69d8ac1dd953c955366abed055976f6dd6d4d2..faab853b7b67177788e76ddb64bc7fc119891aa4 100644
--- a/third_party/WebKit/Source/core/css/CSSPropertyEquality.cpp
+++ b/third_party/WebKit/Source/core/css/CSSPropertyEquality.cpp
@@ -4,6 +4,7 @@
 
 #include "core/css/CSSPropertyEquality.h"
 
+#include "core/css/CSSValue.h"
 #include "core/style/ComputedStyle.h"
 #include "core/style/DataEquivalency.h"
 #include "core/style/ShadowList.h"
@@ -375,4 +376,12 @@ bool CSSPropertyEquality::propertiesEqual(CSSPropertyID prop,
   }
 }
 
+bool CSSPropertyEquality::registeredCustomPropertiesEqual(
+    const AtomicString& propertyName,
+    const ComputedStyle& a,
+    const ComputedStyle& b) {
+  return dataEquivalent(a.getRegisteredVariable(propertyName),
+                        b.getRegisteredVariable(propertyName));
+}
+
 }  // namespace blink