Tentative fix for scroll event related crashes on the NTP

A crash[1] seems to be caused by events attempting to get data from
the NTP while it is not the current page anymore. This CL adds
a check to ensure the page processing the events is the currently
displayed NTP.

[1]: https://crbug.com/649670#c17

BUG=649670

Review-Url: https://codereview.chromium.org/2400163002
Cr-Commit-Position: refs/heads/master@{#423858}

chrome/android/java/src/org/chromium/chrome/browser/ntp/NewTabPage.java

@@ -199,6 +199,11 @@ public class NewTabPage
          *                   just tapped the fakebox.
          */
         void requestUrlFocusFromFakebox(String pastedText);
+
+        /**
+         * @return whether the provided native page is the one currently displayed to the user.
+         */
+        boolean isCurrentPage(NativePage nativePage);
     }
 
     /**
@@ -661,6 +666,13 @@ public class NewTabPage
             mSignInStateObserver = signInStateObserver;
             SigninManager.get(mActivity).addSignInStateObserver(mSignInStateObserver);
         }
+
+        @Override
+        public boolean isCurrentPage() {
+            if (mIsDestroyed) return false;
+            if (mFakeboxDelegate == null) return false;
+            return mFakeboxDelegate.isCurrentPage(NewTabPage.this);
+        }
     };
 
     /**

chrome/android/java/src/org/chromium/chrome/browser/ntp/NewTabPageView.java

@@ -300,6 +300,12 @@ public class NewTabPageView extends FrameLayout
          * 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();
     }
 
     /**
@@ -491,6 +497,12 @@ public class NewTabPageView extends FrameLayout
     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());
         }

chrome/android/java/src/org/chromium/chrome/browser/omnibox/LocationBarLayout.java

@@ -60,6 +60,7 @@ import org.chromium.base.metrics.RecordUserAction;
 import org.chromium.chrome.R;
 import org.chromium.chrome.browser.ChromeActivity;
 import org.chromium.chrome.browser.ChromeSwitches;
+import org.chromium.chrome.browser.NativePage;
 import org.chromium.chrome.browser.WindowDelegate;
 import org.chromium.chrome.browser.appmenu.AppMenuButtonHelper;
 import org.chromium.chrome.browser.ntp.NativePageFactory;
@@ -1134,6 +1135,12 @@ public class LocationBarLayout extends FrameLayout implements OnClickListener,
         }
     }
 
+    @Override
+    public boolean isCurrentPage(NativePage nativePage) {
+        assert nativePage != null;
+        return nativePage == mToolbarDataProvider.getNewTabPageForCurrentTab();
+    }
+
     @Override
     public void showUrlBarCursorWithoutFocusAnimations() {
         if (mUrlHasFocus || mUrlFocusedFromFakebox) return;

chrome/android/javatests/src/org/chromium/chrome/browser/ntp/snippets/ArticleSnippetsTest.java

@@ -358,5 +358,10 @@ public class ArticleSnippetsTest extends ChromeActivityTestCaseBase<ChromeActivi
         public void closeContextMenu() {
             throw new UnsupportedOperationException();
         }
+
+        @Override
+        public boolean isCurrentPage() {
+            return true;
+        }
     }
 }

chrome/android/junit/src/org/chromium/chrome/browser/ntp/cards/NewTabPageAdapterTest.java

@@ -9,8 +9,8 @@ import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertThat;
 import static org.junit.Assert.assertTrue;
 import static org.junit.Assert.fail;
-import static org.mockito.Mockito.any;
-import static org.mockito.Mockito.anyString;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.ArgumentMatchers.anyString;
 import static org.mockito.Mockito.doNothing;
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.spy;
@@ -18,10 +18,6 @@ import static org.mockito.Mockito.times;
 import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.when;
 
-import static org.chromium.base.test.util.Matchers.greaterThanOrEqualTo;
-import static org.chromium.chrome.browser.ntp.cards.ContentSuggestionsTestUtils
-        .createDummySuggestions;
-
 import android.support.annotation.Nullable;
 import android.view.ContextMenu;
 import android.view.Menu;
@@ -34,6 +30,10 @@ import org.junit.runner.RunWith;
 import org.robolectric.RuntimeEnvironment;
 import org.robolectric.annotation.Config;
 
+import static org.chromium.base.test.util.Matchers.greaterThanOrEqualTo;
+import static org.chromium.chrome.browser.ntp.cards.ContentSuggestionsTestUtils
+        .createDummySuggestions;
+
 import org.chromium.base.Callback;
 import org.chromium.base.metrics.RecordHistogram;
 import org.chromium.base.metrics.RecordUserAction;
@@ -1049,5 +1049,10 @@ public class NewTabPageAdapterTest {
         public void registerSignInStateObserver(SignInStateObserver signInStateObserver) {
             mSignInStateObserver = signInStateObserver;
         }
+
+        @Override
+        public boolean isCurrentPage() {
+            return true;
+        }
     }
 }