Correctly reset lastIndex in an RegExp object.

src/runtime.cc

Index: src/runtime.cc
diff --git a/src/runtime.cc b/src/runtime.cc
index ef04ed34f0d8cdff397d6938c4d528a86954ade9..5047dbd49b98366310fc493caeebd25f4d31340e 100644
--- a/src/runtime.cc
+++ b/src/runtime.cc
@@ -1794,7 +1794,8 @@ RUNTIME_FUNCTION(MaybeObject*, Runtime_RegExpInitializeObject) {
         JSRegExp::kIgnoreCaseFieldIndex, ignoreCase, SKIP_WRITE_BARRIER);
     regexp->InObjectPropertyAtPut(
         JSRegExp::kMultilineFieldIndex, multiline, SKIP_WRITE_BARRIER);
-    regexp->ResetLastIndex();
+    regexp->InObjectPropertyAtPut(
+        JSRegExp::kLastIndexFieldIndex, Smi::FromInt(0), SKIP_WRITE_BARRIER);
     return regexp;
   }
 
@@ -2911,7 +2912,7 @@ MUST_USE_RESULT static MaybeObject* StringReplaceAtomRegExpWithString(
 
   int matches = indices.length();
   if (matches == 0) {
-    pattern_regexp->ResetLastIndex();
+    JSRegExp::ResetLastIndex(isolate, pattern_regexp);
     return *subject;
   }
 
@@ -3014,7 +3015,7 @@ MUST_USE_RESULT static MaybeObject* StringReplaceRegExpWithString(
   int32_t* current_match = global_cache.FetchNext();
   if (current_match == NULL) {
     if (global_cache.HasException()) return Failure::Exception();
-    regexp->ResetLastIndex();
+    JSRegExp::ResetLastIndex(isolate, regexp);
     return *subject;
   }
 
@@ -3113,7 +3114,7 @@ MUST_USE_RESULT static MaybeObject* StringReplaceRegExpWithEmptyString(
   int32_t* current_match = global_cache.FetchNext();
   if (current_match == NULL) {
     if (global_cache.HasException()) return Failure::Exception();
-    regexp->ResetLastIndex();
+    JSRegExp::ResetLastIndex(isolate, regexp);
     return *subject;
   }