[Feed v2] Unset RecyclerView.adapter after unbinding

After unbinding from NativeViewListRenderer, we should unset
the adapter of its RecyclerView.

Bug: 1129268
Change-Id: I48a888823647ddcd3e7aad4868d7eb37dec958bd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2422426Reviewed-by: Dan H <harringtond@chromium.org>
Commit-Queue: Jian Li <jianli@chromium.org>
Cr-Commit-Position: refs/heads/master@{#809079}

chrome/android/feed/core/java/src/org/chromium/chrome/browser/feed/v2/NativeViewListRenderer.java

@@ -89,6 +89,8 @@ public class NativeViewListRenderer extends RecyclerView.Adapter<NativeViewListR
     public void unbind() {
         mManager.removeObserver(this);
         onItemRangeRemoved(0, mManager.getItemCount());
+        mView.setAdapter(null);
+        mView.setLayoutManager(null);
         mManager = null;
     }
 

chrome/android/junit/src/org/chromium/chrome/browser/feed/v2/NativeViewListRendererTest.java

@@ -7,6 +7,8 @@ package org.chromium.chrome.browser.feed.v2;
 import static com.google.common.truth.Truth.assertThat;
 
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertNull;
 import static org.mockito.Mockito.times;
 import static org.mockito.Mockito.verify;
 
@@ -97,6 +99,21 @@ public class NativeViewListRendererTest {
         verify(mManager, times(1)).bindNativeView(2, viewHolder.itemView);
     }
 
+    @Test
+    @SmallTest
+    public void testUnbind() {
+        mManager.addContents(
+                0, ImmutableList.of(createContent("1"), createContent("2"), createContent("3")));
+        RecyclerView view = (RecyclerView) mRenderer.bind(mManager);
+        assertNotNull(view.getAdapter());
+        assertNotNull(view.getLayoutManager());
+
+        mRenderer.unbind();
+        assertNull(view.getAdapter());
+        assertNull(view.getLayoutManager());
+        verify(mRenderer, times(1)).notifyItemRangeRemoved(0, 3);
+    }
+
     @Test
     public void testObserver_itemsAddedOnBind() {
         mManager.addContents(