Web MIDI: fix multi-threading problem around message buffer handling

media/midi/midi_manager_mac.cc

Index: media/midi/midi_manager_mac.cc
diff --git a/media/midi/midi_manager_mac.cc b/media/midi/midi_manager_mac.cc
index 7bc8f2332e02f02fbd32342564fcf0eb933397b5..4477944e7738e79734c668ed913825bf073da96d 100644
--- a/media/midi/midi_manager_mac.cc
+++ b/media/midi/midi_manager_mac.cc
@@ -54,7 +54,7 @@ bool MIDIManagerMac::Initialize() {
   result = MIDIInputPortCreate(
       midi_client_,
       CFSTR("MIDI Input"),
-      ReadMidiDispatch,
+      ReadMIDIDispatch,
       this,
       &coremidi_input_);
   if (result != noErr)
@@ -67,10 +67,10 @@ bool MIDIManagerMac::Initialize() {
   if (result != noErr)
     return false;
 
-  int destination_count = MIDIGetNumberOfDestinations();
+  uint32 destination_count = MIDIGetNumberOfDestinations();
   destinations_.resize(destination_count);
 
-  for (int i = 0; i < destination_count ; i++) {
+  for (uint32 i = 0; i < destination_count ; i++) {
     MIDIEndpointRef destination = MIDIGetDestination(i);
 
     // Keep track of all destinations (known as outputs by the Web MIDI API).
@@ -82,9 +82,9 @@ bool MIDIManagerMac::Initialize() {
   }
 
   // Open connections from all sources.
-  int source_count = MIDIGetNumberOfSources();
+  uint32 source_count = MIDIGetNumberOfSources();
 
-  for (int i = 0; i < source_count; ++i)  {
+  for (uint32 i = 0; i < source_count; ++i)  {
     // Receive from all sources.
     MIDIEndpointRef src = MIDIGetSource(i);
     MIDIPortConnectSource(coremidi_input_, src, reinterpret_cast<void*>(src));
@@ -110,7 +110,7 @@ MIDIManagerMac::~MIDIManagerMac() {
     MIDIPortDispose(coremidi_output_);
 }
 
-void MIDIManagerMac::ReadMidiDispatch(const MIDIPacketList* packet_list,
+void MIDIManagerMac::ReadMIDIDispatch(const MIDIPacketList* packet_list,
                                       void* read_proc_refcon,
                                       void* src_conn_refcon) {
   MIDIManagerMac* manager = static_cast<MIDIManagerMac*>(read_proc_refcon);
@@ -121,16 +121,16 @@ void MIDIManagerMac::ReadMidiDispatch(const MIDIPacketList* packet_list,
 #endif
 
   // Dispatch to class method.
-  manager->ReadMidi(source, packet_list);
+  manager->ReadMIDI(source, packet_list);
 }
 
-void MIDIManagerMac::ReadMidi(MIDIEndpointRef source,
+void MIDIManagerMac::ReadMIDI(MIDIEndpointRef source,
                               const MIDIPacketList* packet_list) {
   // Lookup the port index based on the source.
   SourceMap::iterator j = source_map_.find(source);
   if (j == source_map_.end())
     return;
-  int port_index = source_map_[source];
+  uint32 port_index = source_map_[source];
 
   // Go through each packet and process separately.
   for(size_t i = 0; i < packet_list->numPackets; i++) {
@@ -147,10 +147,11 @@ void MIDIManagerMac::ReadMidi(MIDIEndpointRef source,
 }
 
 void MIDIManagerMac::SendMIDIData(MIDIManagerClient* client,
-                                  int port_index,
-                                  const uint8* data,
-                                  size_t length,
+                                  uint32 port_index,
+                                  const std::vector<uint8>& data,
                                   double timestamp) {
+  DCHECK(CurrentlyOnMIDISendThread());
+
   // System Exclusive has already been filtered.
   MIDITimeStamp coremidi_timestamp = SecondsToMIDITimeStamp(timestamp);
 
@@ -159,14 +160,11 @@ void MIDIManagerMac::SendMIDIData(MIDIManagerClient* client,
       kMaxPacketListSize,
       midi_packet_,
       coremidi_timestamp,
-      length,
-      data);
+      data.size(),
+      &data[0]);
 
   // Lookup the destination based on the port index.
-  // TODO(crogers): re-factor |port_index| to use unsigned
-  // to avoid the need for this check.
-  if (port_index < 0 ||
-      static_cast<size_t>(port_index) >= destinations_.size())
+  if (static_cast<size_t>(port_index) >= destinations_.size())
     return;
 
   MIDIEndpointRef destination = destinations_[port_index];
@@ -176,7 +174,7 @@ void MIDIManagerMac::SendMIDIData(MIDIManagerClient* client,
   // Re-initialize for next time.
   midi_packet_ = MIDIPacketListInit(packet_list_);
 
-  client->AccumulateMIDIBytesSent(length);
+  client->AccumulateMIDIBytesSent(data.size());
 }
 
 MIDIPortInfo MIDIManagerMac::GetPortInfoFromEndpoint(