[DevTools] Extract DeviceModeButton from AdvancedApp.

Source/devtools/front_end/emulation/DeviceModeButton.js

Index: Source/devtools/front_end/emulation/DeviceModeButton.js
diff --git a/Source/devtools/front_end/emulation/DeviceModeButton.js b/Source/devtools/front_end/emulation/DeviceModeButton.js
new file mode 100644
index 0000000000000000000000000000000000000000..a69910e17b5ff96f95ffaf066425734137211577
--- /dev/null
+++ b/Source/devtools/front_end/emulation/DeviceModeButton.js
@@ -0,0 +1,67 @@
+// 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);
+    emulationEnabledChanged();
+    overridesWarningUpdated();
+
+    function toggleEmulationEnabled()
+    {
+        WebInspector.overridesSupport.setEmulationEnabled(!button.toggled());
+    }
+
+    function emulationEnabledChanged()
+    {
+        button.setToggled(WebInspector.overridesSupport.emulationEnabled());
+    }
+
+    function overridesWarningUpdated()
+    {
+        var message = WebInspector.overridesSupport.warningMessage();
+        button.setTitle(message || WebInspector.UIString("Toggle device mode"));
+        button.element.classList.toggle("warning", !!message);
+    }
+
+    this._button = button;
+}
+
+WebInspector.DeviceModeButtonProvider.prototype = {
+    /**
+     * @override
+     * @return {?WebInspector.ToolbarItem}
+     */
+    item: function()
+    {
+        return this._button;
+    }
+}
+
+/**
+ * @constructor
+ * @implements {WebInspector.ActionDelegate}
+ */
+WebInspector.ToggleDeviceModeActionDelegate = function()
+{
+}
+
+WebInspector.ToggleDeviceModeActionDelegate.prototype = {
+    /**
+     * @override
+     * @param {!WebInspector.Context} context
+     * @param {string} actionId
+     */
+    handleAction: function(context, actionId)
+    {
+        WebInspector.overridesSupport.setEmulationEnabled(!WebInspector.overridesSupport.emulationEnabled());
+    }
+}