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..63c241b9118683e813eb7f089334416c8661f260 100644
--- a/media/midi/midi_manager_usb.cc
+++ b/media/midi/midi_manager_usb.cc
@@ -43,7 +43,13 @@ 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()) {
+    // |port_index| is provided by a renderer so we can't believe that it is
+    // in the valid range.
+    // TODO(toyoshim): Move this check to MidiHost and kill the renderer when
+    // it fails.
+    return;
+  }
   output_streams_[port_index]->Send(data);
   client->AccumulateMidiBytesSent(data.size());
 }