Disable Microsoft GS Wavetable Synth in Windows 10 Web MIDI backend

media/midi/midi_manager_winrt.cc

Index: media/midi/midi_manager_winrt.cc
diff --git a/media/midi/midi_manager_winrt.cc b/media/midi/midi_manager_winrt.cc
index 11841cbde431cb09c8c6a70dee481c8fe16a081d..c41054574c99dfcd67fe65b542b80cc5c6ab8720 100644
--- a/media/midi/midi_manager_winrt.cc
+++ b/media/midi/midi_manager_winrt.cc
@@ -118,6 +118,18 @@ HRESULT GetPointerToBufferData(IBuffer* buffer, uint8_t** out) {
   return S_OK;
 }
 
+// Checks if given DeviceInformation represent a Microsoft GS Wavetable Synth
+// instance.
+bool IsMicrosoftSynthesizer(IDeviceInformation* info) {
+  auto midi_synthesizer_statics =
+      WrlStaticsFactory<IMidiSynthesizerStatics,
+                        RuntimeClass_Windows_Devices_Midi_MidiSynthesizer>();
+  boolean result = false;
+  HRESULT hr = midi_synthesizer_statics->IsSynthesizer(info, &result);
+  VLOG_IF(1, FAILED(hr)) << "IsSynthesizer failed: " << PrintHr(hr);
+  return result != 0;

[Takashi Toyoshima, 2016/08/31 07:10:21]

|result| is bool from the beginning, right?

[Shao-Chuan Lee, 2016/08/31 07:16:51]

'boolean' is actually unsigned char, casting it to bool with '!= 0' here.

[Takashi Toyoshima, 2016/08/31 07:30:00]

Wow, it isn't standard bool. OK, so as we discussed offline, let's initialize it
with FALSE so that we can easily notice that it's MS specific type, and
probably, it's better in terms of removing implicit cast.

[Shao-Chuan Lee, 2016/08/31 07:42:49]

Done.
https://msdn.microsoft.com/en-us/library/windows/desktop/aa366740(v=vs.85).aspx

+}
+
 // Tokens with value = 0 are considered invalid (as in <wrl/event.h>).
 const int64_t kInvalidTokenValue = 0;
 
@@ -189,6 +201,11 @@ class MidiManagerWinrt::MidiPortManager {
         WRL::Callback<ITypedEventHandler<DeviceWatcher*, DeviceInformation*>>(
             [weak_ptr, task_runner](IDeviceWatcher* watcher,
                                     IDeviceInformation* info) {
+              // Disable Microsoft GS Wavetable Synth due to security reasons.
+              // http://crbug.com/499279
+              if (IsMicrosoftSynthesizer(info))
+                return S_OK;
+
               std::string dev_id = GetIdString(info),
                           dev_name = GetNameString(info);
 
@@ -356,9 +373,6 @@ class MidiManagerWinrt::MidiPortManager {
     DCHECK(thread_checker_.CalledOnValidThread());
     CHECK(is_initialized_);
 
-    // TODO(shaochuan): Disable Microsoft GS Wavetable Synth due to security
-    // reasons. http://crbug.com/499279
-
     port_names_[dev_id] = dev_name;
 
     WRL::Wrappers::HString dev_id_hstring;
@@ -423,6 +437,8 @@ class MidiManagerWinrt::MidiPortManager {
     DCHECK(thread_checker_.CalledOnValidThread());
     CHECK(is_initialized_);
 
+    // Note: in case Microsoft GS Wavetable Synth triggers this event for some
+    // reason, it will be ignored here with log emitted.
     MidiPort<InterfaceType>* port = GetPortByDeviceId(dev_id);
     if (!port) {
       VLOG(1) << "Removing non-existent port " << dev_id;