Opening new "about:blank" tab if all tabs are closed in tab switcher mode.

chrome/android/shell/java/src/org/chromium/chrome/shell/ChromeShellActivity.java

 // 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.
 
 package org.chromium.chrome.shell;
 
 import android.app.Activity;
 import android.content.Intent;
 import android.os.Bundle;
 import android.text.TextUtils;
@@ skipping 276 matching lines @@
         mTabManager.createTab(url, TabLaunchType.FROM_EXTERNAL_APP);
     }
 
     /**
      * Closes all current tabs.
      */
     public void closeAllTabs() {
         mTabManager.closeAllTabs();
     }
 
+    @VisibleForTesting
+    public void closeTab() {
+        mTabManager.closeTab();
+    }
+
     /**
      * Override the menu key event to show AppMenu.
      */
     @Override
     public boolean onKeyDown(int keyCode, KeyEvent event) {
         if (keyCode == KeyEvent.KEYCODE_MENU && event.getRepeatCount() == 0) {
             if (mToolbar != null) mToolbar.hideSuggestions();
             mAppMenuHandler.showAppMenu(findViewById(R.id.menu_button), true, false);
             return true;
         }
@@ skipping 126 matching lines @@
     @VisibleForTesting
     public static void setActivityWindowAndroidFactory(ActivityWindowAndroidFactory factory) {
         sWindowAndroidFactory = factory;
     }
 
     @VisibleForTesting
     public static void setAppMenuHandlerFactory(AppMenuHandlerFactory factory) {
         sAppMenuHandlerFactory = factory;
     }
 }