Fix the tests that change because of change to toISOString format.

test/mjsunit/mirror-date.js

Index: test/mjsunit/mirror-date.js
===================================================================
--- test/mjsunit/mirror-date.js	(revision 3597)
+++ test/mjsunit/mirror-date.js	(working copy)
@@ -57,7 +57,7 @@
 
 // Test Date values.
 testDateMirror(new Date(Date.parse("Dec 25, 1995 1:30 UTC")),
-               "1995-12-25T01:30:00Z");
+               "1995-12-25T01:30:00.000Z");
 d = new Date();
 d.setUTCFullYear(1967);
 d.setUTCMonth(0); // January.
@@ -66,10 +66,12 @@
 d.setUTCMinutes(22);
 d.setUTCSeconds(59);
 d.setUTCMilliseconds(0);
-testDateMirror(d, "1967-01-17T09:22:59Z");
+testDateMirror(d, "1967-01-17T09:22:59.000Z");
 d.setUTCMilliseconds(1);
-testDateMirror(d, "1967-01-17T09:22:59Z");
+testDateMirror(d, "1967-01-17T09:22:59.001Z");
 d.setUTCSeconds(12);
-testDateMirror(d, "1967-01-17T09:22:12Z");
+testDateMirror(d, "1967-01-17T09:22:12.001Z");
 d.setUTCSeconds(36);
-testDateMirror(d, "1967-01-17T09:22:36Z");
+testDateMirror(d, "1967-01-17T09:22:36.001Z");
+d.setUTCMilliseconds(136);
+testDateMirror(d, "1967-01-17T09:22:36.136Z");