linux/mac: Fix race condition when destroying the renderer<->plugin channel

chrome/renderer/webplugin_delegate_proxy.cc

 // Copyright (c) 2006-2008 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 "build/build_config.h"
 
 #if defined(OS_WIN)
 #include <atlbase.h>
@@ skipping 190 matching lines @@
     // The ScriptController deallocates this object independent of its ref count
     // to avoid leaks if the plugin forgets to release it.  So mark the object
     // invalid to avoid accessing it past this point.
     window_script_object_->set_proxy(NULL);
     window_script_object_->set_invalid();
   }
 
   if (channel_host_) {
     channel_host_->RemoveRoute(instance_id_);
     Send(new PluginMsg_DestroyInstance(instance_id_));
+    // Release the channel host now. If we are is the last reference to the
+    // channel, this avoids a race where this renderer asks a new connection to
+    // the same plugin between now and the time 'this' is actually deleted.
+    // Destroying the channel host is what releases the channel name -> FD
+    // association on POSIX, and if we ask for a new connection before it is
+    // released, the plugin will give us a new FD, and we'll assert when trying
+    // to associate it with the channel name.
+    channel_host_ = NULL;

[jam, 2009/08/11 01:37:47]

What about other WebPluginDelegateProxy methods that assume channel_host_ is
non-null and can be called in the meantime (i.e. Paint)?  Don't these functions
need to be updated in this change?

   }
 
   render_view_->PluginDestroyed(this);
   MessageLoop::current()->DeleteSoon(FROM_HERE, this);
 }
 
 bool WebPluginDelegateProxy::Initialize(const GURL& url, char** argn,
                                         char** argv, int argc,
                                         WebPlugin* plugin,
                                         bool load_manually) {
@@ skipping 770 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);
 }