Avoid a CHECK when the modal_loop_pump_messages_event handle comes in as NULL...

chrome/renderer/webplugin_delegate_proxy.cc

 // Copyright (c) 2009 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 "chrome/renderer/webplugin_delegate_proxy.h"
 
 #include <algorithm>
 
 #include "app/gfx/blit.h"
 #include "app/gfx/canvas.h"
@@ skipping 802 matching lines @@
   DCHECK(window_);
   plugin_->WillDestroyWindow(window_);
   window_ = gfx::kNullPluginWindow;
 }
 
 #if defined(OS_WIN)
 void WebPluginDelegateProxy::OnSetWindowlessPumpEvent(
       HANDLE modal_loop_pump_messages_event) {
   DCHECK(modal_loop_pump_messages_event_ == NULL);
 
+  // Bug 25583: this can be null because some "virus scanners" block the
+  // DuplicateHandle call in the plugin process.
+  if (!modal_loop_pump_messages_event)
+    return;
+
   modal_loop_pump_messages_event_.reset(
       new base::WaitableEvent(modal_loop_pump_messages_event));
 }
 #endif
 
 void WebPluginDelegateProxy::OnCancelResource(int id) {
   if (plugin_)
     plugin_->CancelResource(id);
 }
 
@@ skipping 260 matching lines @@
     intptr_t existing_stream, bool notify_needed, intptr_t notify_data) {
   plugin_->InitiateHTTPRangeRequest(url.c_str(), range_info.c_str(),
                                     existing_stream, notify_needed,
                                     notify_data);
 }
 
 void WebPluginDelegateProxy::OnDeferResourceLoading(int resource_id,
                                                     bool defer) {
   plugin_->SetDeferResourceLoading(resource_id, defer);
 }