Teach Blink's IDL parser to handle defaulted sequences of strings.

Source/core/testing/DictionaryTest.h

Index: Source/core/testing/DictionaryTest.h
diff --git a/Source/core/testing/DictionaryTest.h b/Source/core/testing/DictionaryTest.h
index 6e1154eb96a83957539d9e1e1a1974d56a418cdd..7b50f5a7a1c44bfc19c2b7cf7f21e78787cb8c58 100644
--- a/Source/core/testing/DictionaryTest.h
+++ b/Source/core/testing/DictionaryTest.h
@@ -61,6 +61,7 @@ private:
     String m_byteStringMember;
     String m_usvStringMember;
     Nullable<Vector<String>> m_stringSequenceMember;
+    Vector<String> m_stringSequenceMemberWithDefault;
     Nullable<Vector<String>> m_stringSequenceOrNullMember;
     String m_enumMember;
     String m_enumMemberWithDefault;