Add launcherPage.hide() API.

chrome/common/extensions/api/launcher_page.idl

Index: chrome/common/extensions/api/launcher_page.idl
diff --git a/chrome/common/extensions/api/launcher_page.idl b/chrome/common/extensions/api/launcher_page.idl
index a6a1943d42a7bf3fd79f8cd1c0fd3fa537029efc..7e7896a8693666b7d405f8e393cad29c9c66d6d9 100644
--- a/chrome/common/extensions/api/launcher_page.idl
+++ b/chrome/common/extensions/api/launcher_page.idl
@@ -7,6 +7,7 @@
 namespace launcherPage {
   callback PushSubpageCallback = void();
   callback ShowCallback = void();
+  callback HideCallback = void();
   callback SetEnabledCallback = void();
 
   interface Functions {
@@ -24,6 +25,9 @@ namespace launcherPage {
     // 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.