Bring bugfix of global regexps to the 2.1 branch.

src/regexp.js

 // Copyright 2006-2009 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 195 matching lines @@
   if (i < 0 || i > s.length) {
     this.lastIndex = 0;
     return null;
   }
 
   %_Log('regexp', 'regexp-exec,%0r,%1S,%2i', [this, s, lastIndex]);
   // matchIndices is either null or the lastMatchInfo array.
   var matchIndices = %_RegExpExec(this, s, i, lastMatchInfo);
 
   if (matchIndices == null) {
-    if (this.global) this.lastIndex = 0;
+    if (this.global) {
+      this.lastIndex = 0;
+      if (lastIndex != 0) return matchIndices;
+    }
     cache.lastIndex = lastIndex;
     cache.regExp = this;
     cache.subject = s;
     cache.answer = matchIndices;  // Null.
     cache.type = 'exec';
     return matchIndices;        // No match.
   }
 
   var numResults = NUMBER_OF_CAPTURES(lastMatchInfo) >> 1;
   var result;
@@ skipping 292 matching lines @@
   %DefineAccessor($RegExp, "$'", SETTER, NoOpSetter, DONT_ENUM | DONT_DELETE);
 
   for (var i = 1; i < 10; ++i) {
     %DefineAccessor($RegExp, '$' + i, GETTER, RegExpMakeCaptureGetter(i), DONT_DELETE);
     %DefineAccessor($RegExp, '$' + i, SETTER, NoOpSetter, DONT_DELETE);
   }
 }
 
 
 SetupRegExp();