Inctroduce NewStrictSubstring to avoid check for SubString(str, 0, str.length...

src/factory.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 196 matching lines @@
 
 Handle<String> Factory::NewSubString(Handle<String> str,
                                      int begin,
                                      int end) {
   CALL_HEAP_FUNCTION(isolate(),
                      str->SubString(begin, end),
                      String);
 }
 
 
+Handle<String> Factory::NewStrictSubString(Handle<String> str,
+                                           int begin,
+                                           int end) {
+  ASSERT(begin > 0 || end < str->length());
+  CALL_HEAP_FUNCTION(isolate(),
+                     isolate()->heap()->AllocateSubString(*str, begin, end),
+                     String);
+}
+
+
 Handle<String> Factory::NewExternalStringFromAscii(
     ExternalAsciiString::Resource* resource) {
   CALL_HEAP_FUNCTION(
       isolate(),
       isolate()->heap()->AllocateExternalStringFromAscii(resource),
       String);
 }
 
 
 Handle<String> Factory::NewExternalStringFromTwoByte(
@@ skipping 1003 matching lines @@
     Execution::ConfigureInstance(instance,
                                  instance_template,
                                  pending_exception);
   } else {
     *pending_exception = false;
   }
 }
 
 
 } }  // namespace v8::internal