Fix additional spec violations wrt RegExp.lastIndex.

src/runtime.cc

Index: src/runtime.cc
diff --git a/src/runtime.cc b/src/runtime.cc
index 5047dbd49b98366310fc493caeebd25f4d31340e..e8003b6731cc77740ed36596a90a59fcfe957027 100644
--- a/src/runtime.cc
+++ b/src/runtime.cc
@@ -2912,8 +2912,7 @@ MUST_USE_RESULT static MaybeObject* StringReplaceAtomRegExpWithString(
 
   int matches = indices.length();
   if (matches == 0) {
-    JSRegExp::ResetLastIndex(isolate, pattern_regexp);
-    return *subject;
+    return isolate->heap()->undefined_value();
   }
 
   // Detect integer overflow.
@@ -3015,8 +3014,7 @@ MUST_USE_RESULT static MaybeObject* StringReplaceRegExpWithString(
   int32_t* current_match = global_cache.FetchNext();
   if (current_match == NULL) {
     if (global_cache.HasException()) return Failure::Exception();
-    JSRegExp::ResetLastIndex(isolate, regexp);
-    return *subject;
+    return isolate->heap()->undefined_value();
   }
 
   // Guessing the number of parts that the final result string is built
@@ -3114,8 +3112,7 @@ MUST_USE_RESULT static MaybeObject* StringReplaceRegExpWithEmptyString(
   int32_t* current_match = global_cache.FetchNext();
   if (current_match == NULL) {
     if (global_cache.HasException()) return Failure::Exception();
-    JSRegExp::ResetLastIndex(isolate, regexp);
-    return *subject;
+    return isolate->heap()->undefined_value();
   }
 
   int start = current_match[0];