Remove the proxy callback tracker.

ppapi/proxy/dispatcher.cc

Index: ppapi/proxy/dispatcher.cc
diff --git a/ppapi/proxy/dispatcher.cc b/ppapi/proxy/dispatcher.cc
index 8381c6a453ad5664b58f1b5145cfb86dbc9f3ecb..64baef829fe104e89196f0172c3dd0506a829a56 100644
--- a/ppapi/proxy/dispatcher.cc
+++ b/ppapi/proxy/dispatcher.cc
@@ -21,8 +21,7 @@ Dispatcher::Dispatcher(base::ProcessHandle remote_process_handle,
                        GetInterfaceFunc local_get_interface)
     : ProxyChannel(remote_process_handle),
       disallow_trusted_interfaces_(false),  // TODO(brettw) make this settable.
-      local_get_interface_(local_get_interface),
-      callback_tracker_(ALLOW_THIS_IN_INITIALIZER_LIST(this)) {
+      local_get_interface_(local_get_interface) {
 }
 
 Dispatcher::~Dispatcher() {
@@ -55,17 +54,6 @@ void Dispatcher::AddIOThreadMessageFilter(
 }
 
 bool Dispatcher::OnMessageReceived(const IPC::Message& msg) {
-  // Control messages.
-  if (msg.routing_id() == MSG_ROUTING_CONTROL) {
-    bool handled = true;
-    IPC_BEGIN_MESSAGE_MAP(Dispatcher, msg)
-      IPC_MESSAGE_FORWARD(PpapiMsg_ExecuteCallback, &callback_tracker_,
-                          CallbackTracker::ReceiveExecuteSerializedCallback)
-      IPC_MESSAGE_UNHANDLED(handled = false)
-    IPC_END_MESSAGE_MAP()
-    return handled;
-  }
-
   if (msg.routing_id() <= 0 || msg.routing_id() >= INTERFACE_ID_COUNT) {
     OnInvalidMessageReceived();
     return true;