Fix EditingStyle::mergeStyle()'s handling of custom properties

third_party/WebKit/Source/core/editing/EditingStyle.h

Index: third_party/WebKit/Source/core/editing/EditingStyle.h
diff --git a/third_party/WebKit/Source/core/editing/EditingStyle.h b/third_party/WebKit/Source/core/editing/EditingStyle.h
index c5215dc26dd6ca0fd667d201fac5dba21332099b..0c397e984ab6b4b71a662b62eaef3ac1f68de14e 100644
--- a/third_party/WebKit/Source/core/editing/EditingStyle.h
+++ b/third_party/WebKit/Source/core/editing/EditingStyle.h
@@ -34,6 +34,7 @@
 
 #include "core/CSSPropertyNames.h"
 #include "core/CSSValueKeywords.h"
+#include "core/CoreExport.h"
 #include "core/editing/Position.h"
 #include "core/editing/VisibleSelection.h"
 #include "core/editing/WritingDirection.h"
@@ -57,7 +58,7 @@ class QualifiedName;
 class ComputedStyle;
 class StylePropertySet;
 
-class EditingStyle final : public GarbageCollected<EditingStyle> {
+class CORE_EXPORT EditingStyle final : public GarbageCollected<EditingStyle> {
 public:
 
     enum PropertiesToInclude { AllProperties, OnlyEditingInheritableProperties, EditingPropertiesInEffect };