Provide a way for iterating through all external strings referenced from the JS heap

src/api.cc

Index: src/api.cc
===================================================================
--- src/api.cc	(revision 10398)
+++ src/api.cc	(working copy)
@@ -4049,6 +4049,13 @@
 }
 
 
+void v8::V8::VisitExternalResources(ExternalResourceVisitor* visitor) {
+  i::Isolate* isolate = i::Isolate::Current();
+  IsDeadCheck(isolate, "v8::V8::VisitExternalResources");
+  isolate->heap()->VisitExternalResources(visitor);
+}
+
+
 bool v8::V8::IdleNotification(int hint) {
   // Returning true tells the caller that it need not
   // continue to call IdleNotification.