Remove unnecessary code for non-zero-length global regexps.

test/mjsunit/regexp-global.js

Index: test/mjsunit/regexp-global.js
diff --git a/test/mjsunit/regexp-global.js b/test/mjsunit/regexp-global.js
index fac5c6af03fd11dfcb3a4527d948c0e56b47315d..fd61390e0d7ee9956e8abadf5b6028b5b61bfac4 100644
--- a/test/mjsunit/regexp-global.js
+++ b/test/mjsunit/regexp-global.js
@@ -125,3 +125,12 @@ str = str.replace(/(FOUR|TWO) \u817f (GOOD|BAD)/g,
                     return match.length - 7;
                   });
 assertEquals("4, 2!", str);
+
+// Test zero-length matches that have non-zero-length sub-captures that do not
+// start at the match start position.
+str = "up up up up";
+str = str.replace(/\b(?=u(p))/g, function(match, capture) {
+                                    return capture.length;
+                                  });
+
+assertEquals("1up 1up 1up 1up", str);