Add the basic code skeleton for system info event router

chrome/common/extensions/api/experimental_system_info_storage.idl

Index: chrome/common/extensions/api/experimental_system_info_storage.idl
diff --git a/chrome/common/extensions/api/experimental_system_info_storage.idl b/chrome/common/extensions/api/experimental_system_info_storage.idl
index f56d598b12f27a904f84c3f40261b6f37ba7cf17..d8fc5684faada17dd804f4323f30eab803494244 100644
--- a/chrome/common/extensions/api/experimental_system_info_storage.idl
+++ b/chrome/common/extensions/api/experimental_system_info_storage.idl
@@ -25,6 +25,13 @@ namespace experimental.systemInfo.storage {
     double availableCapacity;
   };
 
+  dictionary StorageUnitChangeInfo {
+    // The uniue id of the storage unit already changed.
+    DOMString id;
+    // The new value of the available capacity.
+    double availableCapacity;
+  };
+
   dictionary StorageInfo {
     // The array of storage units connected to the system.
     StorageUnitInfo[] units;
@@ -36,5 +43,22 @@ namespace experimental.systemInfo.storage {
     // Get the storage information from the system.
     static void get(StorageInfoCallback callback);
   };
+
+  interface Events {
+    // Fired when the storage information is updated.
+    // |info|   : The changed information for the specified storage unit
+    static void onAvailableCapacityChanged(StorageUnitChangeInfo info);
+
+    // Fired when a new storage unit is added to the system,
+    // i.e. a new USB disk is plugged in.
+    // |unit| : The information of the new storage unit
+    static void onAdded(StorageUnitInfo unit);
+
+    // Fired when a storage unit is removed from the system
+    // i.e. a USB disk is unplugged
+    // |id| : The unique ID of storage unit already removed
+    static void onRemoved(DOMString id);  
+  };
+ 
 };