Chromium does not throw the exception message by calling NPN_SetException from NPAPI plugin

content/common/npobject_util.cc

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/common/npobject_util.h"
 
 #include "base/string_util.h"
 #include "content/common/np_channel_base.h"
 #include "content/common/npobject_proxy.h"
 #include "content/common/plugin_messages.h"
@@ skipping 69 matching lines @@
                               NPString *script,
                               NPVariant *result) {
   return NPObjectProxy::NPNEvaluate(npp, npobj, script, result);
 }
 
 
 static void NPN_SetExceptionPatch(NPObject *obj, const NPUTF8 *message) {
   std::string message_str(message);
   if (IsPluginProcess()) {
     NPChannelBase* renderer_channel = NPChannelBase::GetCurrentChannel();
-    if (renderer_channel)
-      renderer_channel->Send(new PluginHostMsg_SetException(message_str));
+    if (renderer_channel) {
+      if (obj->_class != NPObjectProxy::npclass()) {
+        int route_id = MSG_ROUTING_NONE;
+        // Determine the route id of NPObjectProxy instance in renderer process
+        // It is the same as the route id of NPObjectStub instance in plugin
+        // process.
+        route_id = renderer_channel->GetExistingRouteForNPObjectStub(obj);
+        renderer_channel->Send(new NPObjectMsg_SetException(route_id,
+                                                            message_str));
+      } else {
+        renderer_channel->Send(new PluginHostMsg_SetException(message_str));
+      }
+    }
   } else {
     WebBindings::setException(obj, message_str.c_str());
   }
 }
 
 static bool NPN_EnumeratePatch(NPP npp, NPObject *obj,
                                NPIdentifier **identifier, uint32_t *count) {
   return NPObjectProxy::NPNEnumerate(obj, identifier, count);
 }
 
@@ skipping 177 matching lines @@
       result->type = NPVariantType_Object;
       result->value.objectValue = npobject_base->GetUnderlyingNPObject();
       WebBindings::retainObject(result->value.objectValue);
       break;
     }
     default:
       NOTREACHED();
   }
   return true;
 }