Make failed capturing parenthesis produce null instead of "".

runtime/lib/regexp_jsc.cc

Index: runtime/lib/regexp_jsc.cc
diff --git a/runtime/lib/regexp_jsc.cc b/runtime/lib/regexp_jsc.cc
index 0066aa7cc5457cac31d25ecc4846878c38d34400..5b34d159d9d67eda519e6cf4d313ff6b506e4d22 100644
--- a/runtime/lib/regexp_jsc.cc
+++ b/runtime/lib/regexp_jsc.cc
@@ -156,13 +156,11 @@ RawArray* Jscre::Execute(const JSRegExp& regex,
 
   const int kMatchPair = 2;

[siva, 2012/03/19 18:29:14]

ASSERT(retval <= (num_bracket_expressions + 1));

   Array& array =
-      Array::Handle(Array::New(kMatchPair * (num_bracket_expressions + 1)));
+      Array::Handle(Array::New(kMatchPair * retval));
   // The matches come in (start, end + 1) pairs for each bracketted expression.
   Smi& start = Smi::Handle();
   Smi& end = Smi::Handle();
-  for (intptr_t i = 0;
-       i < (kMatchPair * (num_bracket_expressions + 1));
-       i += kMatchPair) {
+  for (intptr_t i = 0; i < (kMatchPair * retval); i += kMatchPair) {
     start = Smi::New(offsets[i]);
     end = Smi::New(offsets[i + 1]);
     array.SetAt(i, start);