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

content/common/npobject_proxy.cc

Index: content/common/npobject_proxy.cc
===================================================================
--- content/common/npobject_proxy.cc	(revision 109161)
+++ content/common/npobject_proxy.cc	(working copy)
@@ -62,7 +62,8 @@
     : channel_(channel),
       route_id_(route_id),
       containing_window_(containing_window),
-      page_url_(page_url) {
+      page_url_(page_url),
+      has_exception_thrown_(false) {
   channel_->AddRoute(route_id, this, this);
 }
 
@@ -110,8 +111,15 @@
 }
 
 bool NPObjectProxy::OnMessageReceived(const IPC::Message& msg) {
-  NOTREACHED();
-  return false;
+  bool handled = true;
+
+  IPC_BEGIN_MESSAGE_MAP(NPObjectProxy, msg)
+    IPC_MESSAGE_HANDLER(NPObjectMsg_SetException, OnSetException)
+    IPC_MESSAGE_UNHANDLED(handled = false)
+  IPC_END_MESSAGE_MAP()
+
+  DCHECK(handled);
+  return true;
 }
 
 void NPObjectProxy::OnChannelError() {
@@ -120,6 +128,23 @@
   channel_ = NULL;
 }
 
+void NPObjectProxy::OnSetException(const std::string& msg) {
+  if (IsPluginProcess()) {
+    NOTREACHED() << "Should be only called from renderer process!";
+    return;
+  }
+
+  has_exception_thrown_ = true;
+
+  NPObject* obj = NULL;
+
+  if (channel()) {
+    obj = channel()->GetExistingNPObjectProxy(route_id_);
+  }
+
+  WebKit::WebBindings::setException(obj, msg.c_str());
+}
+
 bool NPObjectProxy::NPHasMethod(NPObject *obj,
                                 NPIdentifier name) {
   if (obj == NULL)
@@ -137,6 +162,7 @@
 
   proxy->Send(new NPObjectMsg_HasMethod(proxy->route_id(), name_param,
                                         &result));
+
   return result;
 }
 
@@ -215,6 +241,14 @@
   GURL page_url = proxy->page_url_;
   proxy->Send(msg);
 
+  // In case of returning result is false and the NPObjectProxy instance
+  // has exception thrown, it means that NPN_SetException is called from
+  // NPAPI plugin during the process of invoking native method.
+  if (!result && proxy->HasExceptionThrown()) {
+    // Tell v8 engine that an exception has been already thrown via np_result
+    BOOLEAN_TO_NPVARIANT(true, *np_result);
+    proxy->SetExceptionThrown(false);
+  }
   // Send may delete proxy.
   proxy = NULL;
 
@@ -435,6 +469,13 @@
   GURL page_url = proxy->page_url_;
   proxy->Send(msg);
 
+  // An exception has been occurred during the process of handling
+  // NPObjectMsg_Construct on the peer side
+  if (!result && proxy->HasExceptionThrown()) {
+    BOOLEAN_TO_NPVARIANT(true, *np_result);
+    proxy->SetExceptionThrown(false);
+  }
+
   // Send may delete proxy.
   proxy = NULL;