MidiManagerUsb should not trust indices provided by renderer.

media/midi/midi_manager_usb.cc

Index: media/midi/midi_manager_usb.cc
diff --git a/media/midi/midi_manager_usb.cc b/media/midi/midi_manager_usb.cc
index fcefdf5a5222891d7bfd1e62a460df67afcdb011..42c1fe84d6b5544f1a202a0fcc3cb8963d836892 100644
--- a/media/midi/midi_manager_usb.cc
+++ b/media/midi/midi_manager_usb.cc
@@ -43,7 +43,11 @@ void MidiManagerUsb::DispatchSendMidiData(MidiManagerClient* client,
                                           uint32_t port_index,
                                           const std::vector<uint8>& data,
                                           double timestamp) {
-  DCHECK_LT(port_index, output_streams_.size());
+  if (port_index >= output_streams_.size()) {

[Takashi Toyoshima, 2015/02/09 06:34:41]

Can you add TODO(toyoshim) here?
I think we should check this in MidiHost, and call BadMessageReceived() to kill
the malicious renderer. But for now, MidiHost does not have information about
the max port number. So this change looks ok now.

[yhirano, 2015/02/09 08:41:12]

Done.

+    // |port_index| is provided by a renderer so we can't believe that it is
+    // in the valid range.
+    return;
+  }
   output_streams_[port_index]->Send(data);
   client->AccumulateMidiBytesSent(data.size());
 }