Add Media device notification to SystemMonitor and Mac impl

base/system_monitor/system_monitor.h

Index: base/system_monitor/system_monitor.h
diff --git a/base/system_monitor/system_monitor.h b/base/system_monitor/system_monitor.h
index 7684523616e0bd787e3a30f5ded9c40e1f7b5371..ca45db3d377c73d83bfd0c59c91648c1c55390f3 100644
--- a/base/system_monitor/system_monitor.h
+++ b/base/system_monitor/system_monitor.h
@@ -8,6 +8,7 @@
 
 #include "base/base_export.h"
 #include "base/basictypes.h"
+#include "base/file_path.h"
 #include "build/build_config.h"
 
 // Windows HiRes timers drain the battery faster so we need to know the battery
@@ -42,6 +43,8 @@ class BASE_EXPORT SystemMonitor {
     RESUME_EVENT        // The system is being resumed.
   };
 
+  typedef unsigned long DeviceIdType;
+
   // Create SystemMonitor. Only one SystemMonitor instance per application
   // is allowed.
   SystemMonitor();
@@ -93,8 +96,19 @@ class BASE_EXPORT SystemMonitor {
   class BASE_EXPORT DevicesChangedObserver {
    public:
     // Notification that the devices connected to the system have changed.
+    // This is only implemented on Windows currently.
     virtual void OnDevicesChanged() {}
 
+    // When a media device is attached or detached, one of these two events
+    // if triggered.
+    // TODO(vandebo) Pass an appropriate device identifier or way to interact
+    // with the devices instead of FilePath.
+    virtual void OnMediaDeviceAttached(const DeviceIdType& id,
+                                       const std::string& name,
+                                       const FilePath& path) {}
+
+    virtual void OnMediaDeviceDetached(const DeviceIdType& id) {}
+
    protected:
     virtual ~DevicesChangedObserver() {}
   };
@@ -123,6 +137,10 @@ class BASE_EXPORT SystemMonitor {
 
   // Cross-platform handling of a device change event.
   void ProcessDevicesChanged();
+  void ProcessMediaDeviceAttached(const DeviceIdType& id,
+                                  const std::string& name,
+                                  const FilePath& path);
+  void ProcessMediaDeviceDetached(const DeviceIdType& id);
 
  private:
 #if defined(OS_MACOSX)
@@ -141,6 +159,10 @@ class BASE_EXPORT SystemMonitor {
 
   // Functions to trigger notifications.
   void NotifyDevicesChanged();
+  void NotifyMediaDeviceAttached(const DeviceIdType& id,
+                                 const std::string& name,
+                                 const FilePath& path);
+  void NotifyMediaDeviceDetached(const DeviceIdType& id);
   void NotifyPowerStateChange();
   void NotifySuspend();
   void NotifyResume();