Make Logger::SuspectReadEvent extract the class name from the object.

src/log.cc

Index: src/log.cc
diff --git a/src/log.cc b/src/log.cc
index d145480f07ae3264df7a7ec1328f63058bcb9275..4fa398c8e2a6a45e17a4a61b68148365dfbba97a 100644
--- a/src/log.cc
+++ b/src/log.cc
@@ -593,12 +593,15 @@ void Logger::ResourceEvent(const char* name, const char* tag) {
 }
 
 
-void Logger::SuspectReadEvent(String* name, String* obj) {
+void Logger::SuspectReadEvent(String* name, Object* obj) {
 #ifdef ENABLE_LOGGING_AND_PROFILING
   if (logfile_ == NULL || !FLAG_log_suspect) return;
+  String* class_name = obj->IsJSObject()
+                       ? JSObject::cast(obj)->class_name()
+                       : Heap::empty_string();
   ScopedLock sl(mutex_);
   fprintf(logfile_, "suspect-read,");
-  obj->PrintOn(logfile_);
+  class_name->PrintOn(logfile_);
   fprintf(logfile_, ",\"");
   name->PrintOn(logfile_);
   fprintf(logfile_, "\"\n");