Fix NaCl plugin shutdown when running the Chrome PPAPI proxy.

webkit/plugins/ppapi/ppapi_plugin_instance.cc

Index: webkit/plugins/ppapi/ppapi_plugin_instance.cc
===================================================================
--- webkit/plugins/ppapi/ppapi_plugin_instance.cc	(revision 151201)
+++ webkit/plugins/ppapi/ppapi_plugin_instance.cc	(working copy)
@@ -402,9 +402,13 @@
   // destroy it. We want to do this prior to calling DidDestroy in case the
   // destructor of the instance object tries to use the instance.
   message_channel_->SetPassthroughObject(NULL);
-  instance_interface_->DidDestroy(pp_instance());
+  // If this is a NaCl plugin instance, shut down the NaCl plugin by calling
+  // its DidDestroy. Don't call DidDestroy on the untrusted plugin instance,
+  // since there is little that it can do at this point.
   if (nacl_plugin_instance_interface_.get())
     nacl_plugin_instance_interface_->DidDestroy(pp_instance());
+  else
+    instance_interface_->DidDestroy(pp_instance());
 
   if (fullscreen_container_) {
     fullscreen_container_->Destroy();
@@ -2142,9 +2146,8 @@
 }
 
 bool PluginInstance::ResetAsProxied() {
-  // Remember the existing instance interface, so we can call DidDestroy in
-  // our Delete() method. This will delete the NaCl plugin instance, which
-  // will shut down the NaCl process.
+  // For NaCl instances, remember the NaCl plugin instance interface, so we
+  // can shut it down by calling its DidDestroy in our Delete() method.
   nacl_plugin_instance_interface_.reset(instance_interface_.release());
 
   base::Callback<const void*(const char*)> get_plugin_interface_func =