Implement 'will-change' parsing

Source/core/css/RuntimeCSSEnabled.cpp

Index: Source/core/css/RuntimeCSSEnabled.cpp
diff --git a/Source/core/css/RuntimeCSSEnabled.cpp b/Source/core/css/RuntimeCSSEnabled.cpp
index d4c8b20c2d933dc9198ba309ad123a0379b44a80..0add9457e0283277bf8135260fedbbc9e6833d2f 100644
--- a/Source/core/css/RuntimeCSSEnabled.cpp
+++ b/Source/core/css/RuntimeCSSEnabled.cpp
@@ -115,6 +115,7 @@ static void setPropertySwitchesFromRuntimeFeatures()
     RuntimeCSSEnabled::setCSSPropertyEnabled(CSSPropertyMaskSourceType, RuntimeEnabledFeatures::cssMaskSourceTypeEnabled());
     RuntimeCSSEnabled::setCSSPropertyEnabled(CSSPropertyColumnFill, RuntimeEnabledFeatures::regionBasedColumnsEnabled());
     RuntimeCSSEnabled::setCSSPropertyEnabled(CSSPropertyScrollBehavior, RuntimeEnabledFeatures::cssomSmoothScrollEnabled());
+    RuntimeCSSEnabled::setCSSPropertyEnabled(CSSPropertyWillChange, RuntimeEnabledFeatures::cssWillChangeEnabled());
 
     // InternalCallback is an implementation detail, rather than an experimental feature, and should never be exposed to the web.
     RuntimeCSSEnabled::setCSSPropertyEnabled(CSSPropertyInternalCallback, false);