RegExp: Fix caching to correctly set lastIndex.

src/regexp.js

Index: src/regexp.js
diff --git a/src/regexp.js b/src/regexp.js
index 566a96c3489ed6c525ac836338ae99c3dae73c74..faa525d62da27ca518e3b4fa8ec12f6ab2cbdaa8 100644
--- a/src/regexp.js
+++ b/src/regexp.js
@@ -186,6 +186,10 @@ function RegExpExec(string) {
       %_IsRegExpEquivalent(cache.regExp, this) &&
       %_ObjectEquals(cache.subject, string)) {
     if (cache.answerSaved) {
+      // If this regexp is not global, cache.lastIndex is zero, so we only get 
+      // here if this.lastIndex is zero, and resulting this.lastIndex
+      // must be zero too, so no change is necessary.
+      if (this.global) this.lastIndex = lastMatchInfo[CAPTURE1];
       return %_RegExpCloneResult(cache.answer);
     } else {
       saveAnswer = true;
@@ -282,6 +286,10 @@ function RegExpTest(string) {
       %_IsRegExpEquivalent(cache.regExp, this) &&
       %_ObjectEquals(cache.subject, string) &&
       %_ObjectEquals(cache.lastIndex, lastIndex)) {
+    // If this regexp is not global, cache.lastIndex is zero, so we only get 
+    // here if this.lastIndex is zero, and resulting this.lastIndex
+    // must be zero too, so no change is necessary.
+    if (this.global) this.lastIndex = lastMatchInfo[CAPTURE1];
     return cache.answer;
   }