Add launcherPage.hide() API.

chrome/common/extensions/api/launcher_page.idl

 // 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.
 
 // The <code>chrome.launcherPage</code> API provides launcher pages in the
 // Chrome Launcher with the capabilities and events they need.
 namespace launcherPage {
   callback PushSubpageCallback = void();
   callback ShowCallback = void();
+  callback HideCallback = void();
   callback SetEnabledCallback = void();
 
   interface Functions {
     // Pushes a subpage state onto a state stack for the launcher page. This
     // state will be popped when the launcher's back button is pressed,
     // preventing the launcher from hiding the launcher page and sending an
     // onPopSubpage event to the launcher page. Once all states are popped, the
     // next press of the back button will cause the launcher to be hidden.
     //
     // Note: All subpages are immediately popped when the launcher is closed or
     // the launcher page is otherwise hidden.
     static void pushSubpage(optional PushSubpageCallback callback);
 
     // Opens the launcher if it isn't currently open and shows the launcher
     // page.
     static void show(optional ShowCallback callback);
 
+    // Returns the launcher to the start page if the launcher page is showing.
+    static void hide(optional HideCallback callback);
+
     // Sets whether the launcher page is enabled in the launcher. If disabled,
     // the launcher page will not be shown when the area at the bottom of the
     // launcher is pressed.
     //
     // Note: The launcher page will still be displayed at the bottom of the
     // launcher's start page and launcherPage.show() will still show the
     // launcher page.
     static void setEnabled(boolean enabled,
                            optional SetEnabledCallback callback);
   };
 
   interface Events {
     // Fired when the launcher page is transitioning between hidden and shown.
     // It's possible for this to be called with a pushed subpage so this
     // event handler should account for transitioning from any subpage to a
     // collapsed view.
     static void onTransitionChanged(double progress);
 
     // Fired when the launcher's back button is pressed if there are remaining
     // subpages on the state stack pushed by pushSubpage().
     static void onPopSubpage();
   };
 };