Add an optional source length field to the Extension constructor.

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 216 matching lines @@
                                            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) {
+    const ExternalAsciiString::Resource* resource) {
   CALL_HEAP_FUNCTION(
       isolate(),
       isolate()->heap()->AllocateExternalStringFromAscii(resource),
       String);
 }
 
 
 Handle<String> Factory::NewExternalStringFromTwoByte(
-    ExternalTwoByteString::Resource* resource) {
+    const ExternalTwoByteString::Resource* resource) {
   CALL_HEAP_FUNCTION(
       isolate(),
       isolate()->heap()->AllocateExternalStringFromTwoByte(resource),
       String);
 }
 
 
 Handle<Context> Factory::NewGlobalContext() {
   CALL_HEAP_FUNCTION(
       isolate(),
@@ skipping 1024 matching lines @@
     Execution::ConfigureInstance(instance,
                                  instance_template,
                                  pending_exception);
   } else {
     *pending_exception = false;
   }
 }
 
 
 } }  // namespace v8::internal