DevTools: add emulation toggle button and splash screen.

Source/devtools/front_end/main/AdvancedApp.js

 // Copyright 2014 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
  * @extends {WebInspector.App}
  */
 WebInspector.AdvancedApp = function()
 {
     WebInspector.App.call(this);
     WebInspector.dockController.addEventListener(WebInspector.DockController.Events.BeforeDockSideChanged, this._openToolboxWindow, this);
 
-    if (!WebInspector.experimentsSettings.responsiveDesign.isEnabled())
-        return;
-
-    this._toggleEmulationButton = new WebInspector.StatusBarButton(WebInspector.UIString("Responsive design and mobile emulation."), "responsive-design-status-bar-item");
+    this._toggleEmulationButton = new WebInspector.StatusBarButton(WebInspector.UIString("Toggle emulation enabled."), "responsive-design-status-bar-item");
     this._toggleEmulationButton.toggled = WebInspector.overridesSupport.settings.emulationEnabled.get();
     this._toggleEmulationButton.addEventListener("click", this._toggleEmulationEnabled, this);
     WebInspector.overridesSupport.settings.emulationEnabled.addChangeListener(this._emulationEnabledChanged, this);
 };
 
 WebInspector.AdvancedApp.prototype = {
     _toggleEmulationEnabled: function()
     {
         WebInspector.overridesSupport.settings.emulationEnabled.set(!this._toggleEmulationButton.toggled);
     },
 
     _emulationEnabledChanged: function()
     {
         this._toggleEmulationButton.toggled = WebInspector.overridesSupport.settings.emulationEnabled.get();
+        if (!WebInspector.experimentsSettings.responsiveDesign.isEnabled() && WebInspector.overridesSupport.settings.emulationEnabled.get())
+            WebInspector.inspectorView.showViewInDrawer("emulation", true);
     },
 
     createRootView: function()
     {
         var rootView = new WebInspector.RootView();
 
         this._rootSplitView = new WebInspector.SplitView(false, true, WebInspector.dockController.canDock() ? "InspectorView.splitViewState" : "InspectorView.dummySplitViewState", 300, 300);
         this._rootSplitView.show(rootView.element);
 
         WebInspector.inspectorView.show(this._rootSplitView.sidebarElement());
@@ skipping 174 matching lines @@
     this._inspectedPagePlaceholder.addEventListener(WebInspector.InspectedPagePlaceholder.Events.Update, advancedApp._onSetInspectedPageBounds.bind(advancedApp, true));
     if (WebInspector.experimentsSettings.responsiveDesign.isEnabled()) {
         this._responsiveDesignView = new WebInspector.ResponsiveDesignView(this._inspectedPagePlaceholder);
         this._responsiveDesignView.show(rootView.element);
     } else {
         this._inspectedPagePlaceholder.show(rootView.element);
     }
     rootView.attachToBody();
     advancedApp._toolboxLoaded(this);
 }