Support toggling Wi-Fi with keyboard shortcut.

chrome/browser/chromeos/system/ash_system_tray_delegate.cc

Index: chrome/browser/chromeos/system/ash_system_tray_delegate.cc
diff --git a/chrome/browser/chromeos/system/ash_system_tray_delegate.cc b/chrome/browser/chromeos/system/ash_system_tray_delegate.cc
index f28867baa85986654352e70b9f980a4e236de086..9c7556a58a654865bd8244161f8b2aa8036cc8fb 100644
--- a/chrome/browser/chromeos/system/ash_system_tray_delegate.cc
+++ b/chrome/browser/chromeos/system/ash_system_tray_delegate.cc
@@ -689,7 +689,11 @@ class SystemTrayDelegate : public ash::SystemTrayDelegate,
   }
 
   virtual void ToggleWifi() OVERRIDE {
+    bool old_wifi_enabled = GetWifiEnabled();
     network_menu_->ToggleWifi();
+    // Use the old state to get the new state because Wi-Fi state is toggled
+    // asynchronously.
+    tray_->network_observer()->OnWifiToggled(!old_wifi_enabled);

[Daniel Erat, 2012/08/02 14:26:45]

Is there any danger of this getting out of sync?

Given NetworkLibrary* lib, GetWifiEnabled() looks like it calls
lib->wifi_enabled() and network_menu_->ToggleWifi() calls
lib->EnableWifiNetworkDevice(!lib->wifi_enabled()).

Are there any other callers of GetWifiEnabled()?  I'm concerned that given
lib->wifi_enabled() == true, someone could call ToggleWifi(), which would result
in network_observer()->OnWifiToggled(false) getting called, but then someone
else could call GetWifiEnabled() soon afterward and get true.

Would it be safer to cache the most-recently-requested state within
SystemTrayDelegate?  Is there any risk of the toggle requests failing?

[mazda, 2012/08/02 17:14:30]

TrayNetwork calls GetWifiEnabled, but it's called in
TrayNetwork::OnNetworkRefresh so it gets the latest state.

I initially tried to cache the wifi state in TrayNetwork and monitor the change
of the state in TrayNetwork::OnNetworkRefresh. It's more reliable than the
current method, but it turned out that it's difficult to distinguish the state
change invoked by the user from the one by the system, which occurs immediately
after the boot. I'd like to identify the state change invoked only by the user.

How about renaming OnWifiToggled to OnWillToggleWifi? This implies more that the
user initiated toggling wifi.

[Daniel Erat, 2012/08/02 17:15:40]

Sure, that sounds great to me.  Thanks!

[mazda, 2012/08/02 19:49:16]

Renamed OnWifiToggled to OnWillToggleWifi.

   }
 
   virtual void ToggleMobile() OVERRIDE {