Separate SuggestionsList into a model and a ModelChangeProcessor

This will allow extracting a mediator that interacts only with the model.

Bug: 847420

Change-Id: I2cfc0f816ae04570dcc12f40757339fc4ed5de0c
Reviewed-on: https://chromium-review.googlesource.com/1142153Reviewed-by: Theresa <twellington@chromium.org>
Commit-Queue: Bernhard Bauer <bauerb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#580489}

chrome/android/java/src/org/chromium/chrome/browser/modelutil/PropertyListObservable.java

+// Copyright 2018 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.modelutil;
+
+import android.support.annotation.Nullable;
+
+import java.util.Collection;
+
+/**
+ * Represents a list of (property-)observable items, and notifies about changes to any of its items.
+ *
+ * @param <T> The type of item in the list.
+ * @param <P> The property key type for {@code T} to be used as payload for partial updates.
+ */
+public class PropertyListObservable<T extends PropertyObservable<P>, P>
+        extends SimpleListObservableBase<T, P> {
+    private final PropertyObservable.PropertyObserver<P> mPropertyObserver =
+            this::onPropertyChanged;
+
+    @Override
+    public void add(T item) {
+        super.add(item);
+        item.addObserver(mPropertyObserver);
+    }
+
+    @Override
+    public void remove(T item) {
+        item.removeObserver(mPropertyObserver);
+        super.remove(item);
+    }
+
+    @Override
+    public void update(int index, T item) {
+        get(index).removeObserver(mPropertyObserver);
+        super.update(index, item);
+        item.addObserver(mPropertyObserver);
+    }
+
+    @Override
+    public void set(Collection<T> newItems) {
+        for (T item : this) {
+            item.removeObserver(mPropertyObserver);
+        }
+        super.set(newItems);
+        for (T item : newItems) {
+            item.addObserver(mPropertyObserver);
+        }
+    }
+
+    private void onPropertyChanged(PropertyObservable<P> source, @Nullable P propertyKey) {
+        notifyItemChanged(indexOf(source), propertyKey);
+    }
+}

chrome/android/java/src/org/chromium/chrome/browser/modelutil/SimpleListObservableBase.java

@@ -77,10 +77,12 @@ public class SimpleListObservableBase<T, P> extends ListObservableImpl<P> implem
     /**
      * Removes an item by position from the held {@link List}. Notifies observers about the removal.
      * @param position The position of the item to be removed.
+     * @return The item that has been removed.
      */
-    public void removeAt(int position) {
-        mItems.remove(position);
+    public T removeAt(int position) {
+        T item = mItems.remove(position);
         notifyItemRemoved(position);
+        return item;
     }
 
     /**

chrome/android/java/src/org/chromium/chrome/browser/ntp/snippets/SnippetArticle.java

@@ -9,6 +9,8 @@ import android.support.annotation.ColorInt;
 import android.support.annotation.Nullable;
 
 import org.chromium.base.DiscardableReferencePool.DiscardableReference;
+import org.chromium.chrome.browser.modelutil.PropertyObservable;
+import org.chromium.chrome.browser.ntp.cards.NewTabPageViewHolder.PartialBindCallback;
 import org.chromium.chrome.browser.suggestions.OfflinableSuggestion;
 
 import java.io.File;
@@ -16,7 +18,8 @@ import java.io.File;
 /**
  * Represents the data for an article card on the NTP.
  */
-public class SnippetArticle implements OfflinableSuggestion {
+public class SnippetArticle
+        extends PropertyObservable<PartialBindCallback> implements OfflinableSuggestion {
     /** The category of this article. */
     public final int mCategory;
 

chrome/android/java_sources.gni

@@ -809,6 +809,7 @@ chrome_java_sources = [
   "java/src/org/chromium/chrome/browser/modelutil/ListObservable.java",
   "java/src/org/chromium/chrome/browser/modelutil/ListObservableImpl.java",
   "java/src/org/chromium/chrome/browser/modelutil/PropertyKey.java",
+  "java/src/org/chromium/chrome/browser/modelutil/PropertyListObservable.java",
   "java/src/org/chromium/chrome/browser/modelutil/PropertyModel.java",
   "java/src/org/chromium/chrome/browser/modelutil/PropertyModelChangeProcessor.java",
   "java/src/org/chromium/chrome/browser/modelutil/PropertyObservable.java",

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

@@ -16,6 +16,7 @@ import static org.junit.Assert.assertTrue;
 import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.ArgumentMatchers.anyBoolean;
 import static org.mockito.ArgumentMatchers.anyInt;
+import static org.mockito.ArgumentMatchers.anyString;
 import static org.mockito.ArgumentMatchers.eq;
 import static org.mockito.ArgumentMatchers.same;
 import static org.mockito.Mockito.doNothing;
@@ -576,6 +577,7 @@ public class SuggestionsSectionTest {
             @SuppressWarnings("unchecked")
             Callback<String> callback = mock(Callback.class);
             section.dismissItem(1, callback);
+            verify(callback).onResult(anyString());
         }
         assertEquals(0, section.getSuggestionsCount());