Tentative fix for scroll event related crashes on the NTP

chrome/android/java/src/org/chromium/chrome/browser/ntp/NewTabPageView.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.ntp;
 
 import android.annotation.SuppressLint;
 import android.content.Context;
 import android.content.res.Configuration;
 import android.content.res.Resources;
@@ skipping 282 matching lines @@
          * invalidated (has destroy() called) when the NewTabPage is destroyed so use this method
          * instead of keeping your own reference.
          */
         @Nullable SuggestionsSource getSuggestionsSource();
 
         /**
          * Registers a {@link SignInStateObserver}, will handle the de-registration when the New Tab
          * Page goes away.
          */
         void registerSignInStateObserver(SignInStateObserver signInStateObserver);
+
+        /**
+         * @return whether the {@link NewTabPage} associated with this manager is the current page
+         * displayed to the user.
+         */
+        boolean isCurrentPage();
     }
 
     /**
      * Default constructor required for XML inflation.
      */
     public NewTabPageView(Context context, AttributeSet attrs) {
         super(context, attrs);
     }
 
     /**
@@ skipping 171 matching lines @@
                 public void onClick(View v) {
                     mManager.navigateToBookmarks();
                 }
             });
         }
     }
 
     private void updateSearchBoxOnScroll() {
         if (mDisableUrlFocusChangeAnimations) return;
 
+        // When the page changes (tab switching or new page loading), it is possible that events
+        // (e.g. delayed RecyclerView change notifications) trigger calls to these methods after
+        // the current page changes. We check it again to make sure we don't attempt to update the
+        // wrong page.
+        if (!mManager.isCurrentPage()) return;
+
         if (mSearchBoxScrollListener != null) {
             mSearchBoxScrollListener.onNtpScrollChanged(getToolbarTransitionPercentage());
         }
     }
 
     /**
      * Calculates the percentage (between 0 and 1) of the transition from the search box to the
      * omnibox at the top of the New Tab Page, which is determined by the amount of scrolling and
      * the position of the search box.
      *
@@ skipping 714 matching lines @@
     }
 
     /**
      * @return The adapter position the user has scrolled to.
      */
     public int getScrollPosition() {
         if (mUseCardsUi) return mRecyclerView.getScrollPosition();
         return RecyclerView.NO_POSITION;
     }
 }