Correct handling of named optional parameters with noSuchMethod invocations.

runtime/vm/dart_entry.cc

Index: runtime/vm/dart_entry.cc
===================================================================
--- runtime/vm/dart_entry.cc	(revision 24876)
+++ runtime/vm/dart_entry.cc	(working copy)
@@ -167,15 +167,22 @@
 }
 
 
-bool ArgumentsDescriptor::MatchesNameAt(intptr_t index,
-                                        const String& other) const {
+RawString* ArgumentsDescriptor::NameAt(intptr_t index) const {
   const intptr_t offset = kFirstNamedEntryIndex +
                           (index * kNamedEntrySize) +
                           kNameOffset;
-  return array_.At(offset) == other.raw();
+  String& result = String::Handle();
+  result ^= array_.At(offset);
+  return result.raw();
 }
 
 
+bool ArgumentsDescriptor::MatchesNameAt(intptr_t index,
+                                        const String& other) const {
+  return NameAt(index) == other.raw();
+}
+
+
 intptr_t ArgumentsDescriptor::count_offset() {
   return Array::element_offset(kCountIndex);
 }