[DevTools] Show warning on device mode button when network throttling is enabled.

Source/devtools/front_end/emulation/DeviceModeButton.js

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 /**
  * @constructor
  * @implements {WebInspector.ToolbarItem.Provider}
  */
 WebInspector.DeviceModeButtonProvider = function()
 {
     var button = new WebInspector.ToolbarButton(WebInspector.UIString("Toggle device mode"), "emulation-toolbar-item");
     button.addEventListener("click", toggleEmulationEnabled);
     WebInspector.overridesSupport.addEventListener(WebInspector.OverridesSupport.Events.EmulationStateChanged, emulationEnabledChanged);
-    WebInspector.overridesSupport.addEventListener(WebInspector.OverridesSupport.Events.OverridesWarningUpdated, overridesWarningUpdated);
+    WebInspector.overridesSupport.addEventListener(WebInspector.OverridesSupport.Events.OverridesWarningUpdated, updateWarning);
+    var networkConditionsSetting = WebInspector.moduleSetting("networkConditions");
+    networkConditionsSetting.addChangeListener(updateWarning);
+
     emulationEnabledChanged();
-    overridesWarningUpdated();
+    updateWarning();
 
     function toggleEmulationEnabled()
     {
         WebInspector.overridesSupport.setEmulationEnabled(!button.toggled());
     }
 
     function emulationEnabledChanged()
     {
         button.setToggled(WebInspector.overridesSupport.emulationEnabled());
     }
 
-    function overridesWarningUpdated()
+    function updateWarning()
     {
         var message = WebInspector.overridesSupport.warningMessage();
+        if (!message && networkConditionsSetting.get().throughput >= 0)
+            message = WebInspector.UIString("Network throttling is enabled");
         button.setTitle(message || WebInspector.UIString("Toggle device mode"));
         button.element.classList.toggle("warning", !!message);
     }
 
     this._button = button;
 }
 
 WebInspector.DeviceModeButtonProvider.prototype = {
     /**
      * @override
@@ skipping 17 matching lines @@
     /**
      * @override
      * @param {!WebInspector.Context} context
      * @param {string} actionId
      */
     handleAction: function(context, actionId)
     {
         WebInspector.overridesSupport.setEmulationEnabled(!WebInspector.overridesSupport.emulationEnabled());
     }
 }