Tab manager view should hide on press of back key

chrome/android/shell/java/src/org/chromium/chrome/shell/ChromeShellTabModelSelector.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.view.LayoutInflater;
 import android.view.ViewGroup;
 import android.view.ViewParent;
 
@@ skipping 119 matching lines @@
                     mParent.getContext()).inflate(R.layout.accessibility_tab_switcher, null);
             mTabModelWrapper.setup(null);
             mTabModelWrapper.setTabModelSelector(this);
         }
 
         if (mTabModelWrapper.getParent() == null) {
             mParent.addView(mTabModelWrapper);
         }
     }
 
-    private boolean isTabSwitcherVisible() {
+    public boolean isTabSwitcherVisible() {
         return mTabModelWrapper != null && mTabModelWrapper.getParent() == mParent;
     }
 }