clang/win: Work around in-class initializer bug.

Source/core/css/resolver/MatchResult.h

Index: Source/core/css/resolver/MatchResult.h
diff --git a/Source/core/css/resolver/MatchResult.h b/Source/core/css/resolver/MatchResult.h
index eee39dbff2d505e386f6f0dafcc81b1f317604d5..342f4fb1a3eaffb335c6c34967d8f49d55f30029 100644
--- a/Source/core/css/resolver/MatchResult.h
+++ b/Source/core/css/resolver/MatchResult.h
@@ -87,6 +87,8 @@ private:
 class CORE_EXPORT MatchResult {
     STACK_ALLOCATED();
 public:
+    MatchResult();
+
     void addMatchedProperties(const StylePropertySet* properties, unsigned linkMatchType = CSSSelector::MatchAll, PropertyWhitelistType = PropertyWhitelistNone);
     bool hasMatchedProperties() const { return m_matchedProperties.size(); }