Maintain the invariant that the pattern string in an atom regexp is always ...

src/runtime.cc

Index: src/runtime.cc
===================================================================
--- src/runtime.cc	(revision 5888)
+++ src/runtime.cc	(working copy)
@@ -2019,10 +2019,7 @@
   }
 
   Handle<JSArray> GetParts() {
-    Handle<JSArray> result =
-        Factory::NewJSArrayWithElements(array_builder_.array());
-    result->set_length(Smi::FromInt(array_builder_.length()));
-    return result;
+    return array_builder_.ToJSArray();
   }
 
  private:
@@ -2597,7 +2594,7 @@
 
 // Perform string match of pattern on subject, starting at start index.
 // Caller must ensure that 0 <= start_index <= sub->length(),
-// and should check that pat->length() + start_index <= sub->length()
+// and should check that pat->length() + start_index <= sub->length().
 int Runtime::StringMatch(Handle<String> sub,
                          Handle<String> pat,
                          int start_index) {
@@ -3196,7 +3193,7 @@
   if (regexp->TypeTag() == JSRegExp::ATOM) {
     Handle<String> pattern(
         String::cast(regexp->DataAt(JSRegExp::kAtomPatternIndex)));
-    if (!pattern->IsFlat()) FlattenString(pattern);
+    ASSERT(pattern->IsFlat());
     if (SearchStringMultiple(subject, pattern, last_match_info, &builder)) {
       return *builder.ToJSArray(result_array);
     }