Convert SVGSMILElement::resolveInterval to return an SMILInterval

Source/core/svg/animation/SVGSMILElement.h

Index: Source/core/svg/animation/SVGSMILElement.h
diff --git a/Source/core/svg/animation/SVGSMILElement.h b/Source/core/svg/animation/SVGSMILElement.h
index 5404dd13aec8fbf31a6fe9d2b0dc2989d96bd8ac..38ad8985000d7b8671d3ed74c9c6d094a8b0a138 100644
--- a/Source/core/svg/animation/SVGSMILElement.h
+++ b/Source/core/svg/animation/SVGSMILElement.h
@@ -147,9 +147,15 @@ private:
     };
 
     SMILTime findInstanceTime(BeginOrEnd, SMILTime minimumTime, bool equalsMinimumOK) const;
+
+    enum ResolveInterval {
+        FirstInterval,
+        NextInterval
+    };
+
+    SMILInterval resolveInterval(ResolveInterval) const;
     void resolveFirstInterval();
     bool resolveNextInterval();
-    void resolveInterval(bool first, SMILTime& beginResult, SMILTime& endResult) const;
     SMILTime resolveActiveEnd(SMILTime resolvedBegin, SMILTime resolvedEnd) const;
     SMILTime repeatingDuration() const;