Support toggling Wi-Fi with keyboard shortcut.

ash/system/network/network_observer.h

Index: ash/system/network/network_observer.h
diff --git a/ash/system/network/network_observer.h b/ash/system/network/network_observer.h
index f55a71adc1ea5912a5b651a48a124f10474e0fc3..0b5b550c5f77c45e7f8c343aa72cc1fbdf4f9680 100644
--- a/ash/system/network/network_observer.h
+++ b/ash/system/network/network_observer.h
@@ -42,6 +42,10 @@ class NetworkObserver {
                                const string16& link_text) = 0;
   // Clears the error notification for |error_type|.
   virtual void ClearNetworkError(ErrorType error_type) = 0;
+
+  // Called when the user toggled Wi-Fi enable/disable.
+  // |wifi_enabled| is the new state of Wi-Fi after it is toggled.
+  virtual void OnWifiToggled(bool wifi_enabled) = 0;
 };
 
 }  // namespace ash