Faster string.replace with regexp pattern.

src/jsregexp.h

Index: src/jsregexp.h
diff --git a/src/jsregexp.h b/src/jsregexp.h
index bb28f06a98c17904987c3a57898cf2419556a665..327016cbc0f333ab7c9e11f2fbdb6975adee2ae7 100644
--- a/src/jsregexp.h
+++ b/src/jsregexp.h
@@ -36,6 +36,13 @@ class RegExpMacroAssembler;
 
 class RegExpImpl {
  public:
+  static inline bool UseNativeRegexp() {
+#ifdef ARM
+    return false;
+#else
+    return FLAG_regexp_native;
+#endif
+  }
   // Creates a regular expression literal in the old space.
   // This function calls the garbage collector if necessary.
   static Handle<Object> CreateRegExpLiteral(Handle<JSFunction> constructor,