Manage MIDI related objects and sessions' lifecycles correctly

content/browser/media/midi_host.h

Index: content/browser/media/midi_host.h
diff --git a/content/browser/media/midi_host.h b/content/browser/media/midi_host.h
index ef5f904b5de7d50178e4de095d71b78c6e3aca38..714444c9d7dfa3b20ddf48a3d71e107b5d0d3417 100644
--- a/content/browser/media/midi_host.h
+++ b/content/browser/media/midi_host.h
@@ -11,6 +11,7 @@
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/scoped_vector.h"
+#include "base/synchronization/lock.h"
 #include "content/common/content_export.h"
 #include "content/public/browser/browser_message_filter.h"
 #include "content/public/browser/browser_thread.h"
@@ -35,8 +36,7 @@ class CONTENT_EXPORT MidiHost
   virtual bool OnMessageReceived(const IPC::Message& message) override;
 
   // MidiManagerClient implementation.
-  virtual void CompleteStartSession(int client_id,
-                                    media::MidiResult result) override;
+  virtual void CompleteStartSession(media::MidiResult result) override;
   virtual void ReceiveMidiData(uint32 port,
                                const uint8* data,
                                size_t length,
@@ -44,13 +44,15 @@ class CONTENT_EXPORT MidiHost
   virtual void AccumulateMidiBytesSent(size_t n) override;
 
   // Start session to access MIDI hardware.
-  void OnStartSession(int client_id);
+  void OnStartSession();
 
   // Data to be sent to a MIDI output port.
   void OnSendData(uint32 port,
                   const std::vector<uint8>& data,
                   double timestamp);
 
+  void OnEndSession();
+
  private:
   FRIEND_TEST_ALL_PREFIXES(MidiHostTest, IsValidWebMIDIData);
   friend class base::DeleteHelper<MidiHost>;
@@ -71,6 +73,9 @@ class CONTENT_EXPORT MidiHost
   // messages.
   bool has_sys_ex_permission_;
 
+  // Represents if a session is requested to start.
+  bool is_session_requested_;
+
   // |midi_manager_| talks to the platform-specific MIDI APIs.
   // It can be NULL if the platform (or our current implementation)
   // does not support MIDI.  If not supported then a call to