Last_n: do not save snapshot of custom tabs.

chrome/android/javatests/src/org/chromium/chrome/browser/customtabs/CustomTabActivityTestBase.java

 // Copyright 2015 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.browser.customtabs;
 
 import static org.chromium.base.test.util.ScalableTimeout.scaleTimeout;
 
 import android.app.Activity;
 import android.content.Intent;
@@ skipping 79 matching lines @@
             fail();
         }
         CriteriaHelper.pollUiThread(new Criteria("Deferred startup never completed") {
             @Override
             public boolean isSatisfied() {
                 return DeferredStartupHandler.getInstance().isDeferredStartupCompleteForApp();
             }
         }, STARTUP_TIMEOUT_MS, CriteriaHelper.DEFAULT_POLLING_INTERVAL);
         assertNotNull(tab);
         assertNotNull(tab.getView());
+        assertTrue(tab.isCurrentlyACustomTab());
     }
 }