Setup base structure for contextual suggestions UI component

Create the basic MVC components for the contextual suggestions component
and content sub-component. Sets up basic connection to the bottom sheet
and moves some prototype code to the ContextualSuggestionsMediator.

A follow-up CL will remove the old, dead prototype code.

BUG=822842

Change-Id: I01461f5ae4c5ec0cc33dbad31daa1415fe46c2cf
Reviewed-on: https://chromium-review.googlesource.com/967010
Commit-Queue: Theresa <twellington@chromium.org>
Reviewed-by: Bernhard Bauer <bauerb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#544737}

chrome/android/java/res/layout/contextual_suggestions_layout.xml

+<?xml version="1.0" encoding="utf-8"?>
+<!-- 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. -->
+
+<org.chromium.chrome.browser.suggestions.SuggestionsRecyclerView
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    android:scrollbars="vertical"
+    android:paddingTop="@dimen/bottom_control_container_height" />
\ No newline at end of file

chrome/android/java/src/org/chromium/chrome/browser/ChromeActivity.java

@@ -69,6 +69,7 @@ import org.chromium.chrome.browser.compositor.layouts.content.TabContentManager;
 import org.chromium.chrome.browser.contextualsearch.ContextualSearchFieldTrial;
 import org.chromium.chrome.browser.contextualsearch.ContextualSearchManager;
 import org.chromium.chrome.browser.contextualsearch.ContextualSearchManager.ContextualSearchTabPromotionDelegate;
+import org.chromium.chrome.browser.contextualsuggestions.ContextualSuggestionsCoordinator;
 import org.chromium.chrome.browser.datausage.DataUseTabUIManager;
 import org.chromium.chrome.browser.device.DeviceClassManager;
 import org.chromium.chrome.browser.dom_distiller.DomDistillerUIUtils;
@@ -115,7 +116,6 @@ import org.chromium.chrome.browser.snackbar.DataReductionPromoSnackbarController
 import org.chromium.chrome.browser.snackbar.DataUseSnackbarController;
 import org.chromium.chrome.browser.snackbar.SnackbarManager;
 import org.chromium.chrome.browser.snackbar.SnackbarManager.SnackbarManageable;
-import org.chromium.chrome.browser.suggestions.ContextualSuggestionsManager;
 import org.chromium.chrome.browser.sync.ProfileSyncService;
 import org.chromium.chrome.browser.sync.SyncController;
 import org.chromium.chrome.browser.tab.Tab;
@@ -258,7 +258,7 @@ public abstract class ChromeActivity extends AsyncInitializationActivity
     private ToolbarManager mToolbarManager;
     private FindToolbarManager mFindToolbarManager;
     private BottomSheet mBottomSheet;
-    private ContextualSuggestionsManager mContextualSuggestionsManager;
+    private ContextualSuggestionsCoordinator mContextualSuggestionsCoordinator;
     private FadingBackgroundView mFadingBackgroundView;
 
     // Time in ms that it took took us to inflate the initial layout
@@ -1134,6 +1134,11 @@ public abstract class ChromeActivity extends AsyncInitializationActivity
             mBottomSheet = null;
         }
 
+        if (mContextualSuggestionsCoordinator != null) {
+            mContextualSuggestionsCoordinator.destroy();
+            mContextualSuggestionsCoordinator = null;
+        }
+
         if (mTabModelsInitialized) {
             TabModelSelector selector = getTabModelSelector();
             if (selector != null) selector.destroy();
@@ -1259,8 +1264,8 @@ public abstract class ChromeActivity extends AsyncInitializationActivity
             });
             mFadingBackgroundView.addObserver(mBottomSheet);
 
-            mContextualSuggestionsManager = new ContextualSuggestionsManager(
-                    this, mBottomSheet, getTabModelSelector(), getSnackbarManager());
+            mContextualSuggestionsCoordinator =
+                    new ContextualSuggestionsCoordinator(this, mBottomSheet, getTabModelSelector());
         }
     }
 

chrome/android/java/src/org/chromium/chrome/browser/contextualsuggestions/ContentCoordinator.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.contextualsuggestions;
+
+import android.content.Context;
+import android.view.LayoutInflater;
+import android.view.View;
+import android.view.ViewGroup;
+
+import org.chromium.chrome.R;
+import org.chromium.chrome.browser.modelutil.RecyclerViewModelChangeProcessor;
+import org.chromium.chrome.browser.ntp.snippets.SnippetArticle;
+import org.chromium.chrome.browser.profiles.Profile;
+import org.chromium.chrome.browser.suggestions.SuggestionsRecyclerView;
+import org.chromium.chrome.browser.suggestions.SuggestionsUiDelegate;
+import org.chromium.chrome.browser.widget.displaystyle.UiConfig;
+
+/**
+ * Coordinator for the content sub-component. Responsible for communication with the parent
+ * {@link ContextualSuggestionsCoordinator} and lifecycle of component objects.
+ */
+class ContentCoordinator {
+    private final ContextualSuggestionsModel mModel;
+
+    private SuggestionsRecyclerView mRecyclerView;
+    private RecyclerViewModelChangeProcessor<SnippetArticle, ContextualSuggestionCardViewHolder>
+            mModelChangeProcessor;
+
+    /**
+     * Construct a new {@link ContentCoordinator}.
+     * @param context The {@link Context} used to retrieve resources.
+     * @param parentView The parent {@link View} to which the content will eventually be attached.
+     * @param profile The regular {@link Profile}.
+     * @param uiDelegate The {@link SuggestionsUiDelegate} used to help construct items in the
+     *                   content view.
+     * @param model The {@link ContextualSuggestionsModel} for the component.
+     */
+    ContentCoordinator(Context context, ViewGroup parentView, Profile profile,
+            SuggestionsUiDelegate uiDelegate, ContextualSuggestionsModel model) {
+        mModel = model;
+
+        mRecyclerView = (SuggestionsRecyclerView) LayoutInflater.from(context).inflate(
+                R.layout.contextual_suggestions_layout, parentView, false);
+
+        ContextualSuggestionsAdapter adapter = new ContextualSuggestionsAdapter(
+                context, profile, new UiConfig(mRecyclerView), uiDelegate, mModel);
+        mRecyclerView.setAdapter(adapter);
+
+        mModelChangeProcessor = new RecyclerViewModelChangeProcessor<>(adapter);
+        mModel.addObserver(mModelChangeProcessor);
+    }
+
+    /** @return The content {@link View}. */
+    View getView() {
+        return mRecyclerView;
+    }
+
+    /** @return The vertical scroll offset of the content view. */
+    int getVerticalScrollOffset() {
+        return mRecyclerView.computeVerticalScrollOffset();
+    }
+
+    /** Destroy the content component. */
+    void destroy() {
+        if (mRecyclerView == null) return;
+
+        mRecyclerView.setAdapter(null);
+        mRecyclerView = null;
+
+        mModel.removeObserver(mModelChangeProcessor);
+        mModelChangeProcessor = null;
+    }
+}

chrome/android/java/src/org/chromium/chrome/browser/contextualsuggestions/ContextualSuggestionCardViewHolder.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.contextualsuggestions;
+
+import org.chromium.chrome.browser.ntp.ContextMenuManager;
+import org.chromium.chrome.browser.ntp.snippets.SnippetArticleViewHolder;
+import org.chromium.chrome.browser.offlinepages.OfflinePageBridge;
+import org.chromium.chrome.browser.suggestions.SuggestionsRecyclerView;
+import org.chromium.chrome.browser.suggestions.SuggestionsUiDelegate;
+import org.chromium.chrome.browser.widget.displaystyle.UiConfig;
+
+/** Holder for a contextual suggestions card. **/
+public class ContextualSuggestionCardViewHolder extends SnippetArticleViewHolder {
+    ContextualSuggestionCardViewHolder(SuggestionsRecyclerView parent,
+            ContextMenuManager contextMenuManager, SuggestionsUiDelegate uiDelegate,
+            UiConfig uiConfig, OfflinePageBridge offlinePageBridge) {
+        super(parent, contextMenuManager, uiDelegate, uiConfig, offlinePageBridge);
+    }
+
+    @Override
+    public boolean isDismissable() {
+        return false;
+    }
+}

chrome/android/java/src/org/chromium/chrome/browser/contextualsuggestions/ContextualSuggestionsAdapter.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.contextualsuggestions;
+
+import android.content.Context;
+import android.support.v7.widget.RecyclerView;
+import android.view.ViewGroup;
+
+import org.chromium.chrome.R;
+import org.chromium.chrome.browser.modelutil.RecyclerViewAdapter;
+import org.chromium.chrome.browser.ntp.cards.ItemViewType;
+import org.chromium.chrome.browser.ntp.cards.SuggestionsCategoryInfo;
+import org.chromium.chrome.browser.ntp.snippets.ContentSuggestionsCardLayout;
+import org.chromium.chrome.browser.ntp.snippets.KnownCategories;
+import org.chromium.chrome.browser.ntp.snippets.SnippetArticle;
+import org.chromium.chrome.browser.offlinepages.OfflinePageBridge;
+import org.chromium.chrome.browser.profiles.Profile;
+import org.chromium.chrome.browser.suggestions.ContentSuggestionsAdditionalAction;
+import org.chromium.chrome.browser.suggestions.SuggestionsRecyclerView;
+import org.chromium.chrome.browser.suggestions.SuggestionsUiDelegate;
+import org.chromium.chrome.browser.widget.displaystyle.UiConfig;
+
+/**
+ * An adapter that contains the view binder for the content component.
+ */
+class ContextualSuggestionsAdapter
+        extends RecyclerViewAdapter<SnippetArticle, ContextualSuggestionCardViewHolder> {
+    private class ContextualSuggestionsViewBinder
+            implements ViewBinder<SnippetArticle, ContextualSuggestionCardViewHolder> {
+        @Override
+        public ContextualSuggestionCardViewHolder onCreateViewHolder(
+                ViewGroup parent, int viewType) {
+            assert viewType == ItemViewType.SNIPPET;
+
+            // TODO(twellington): Hook up ContextMenuManager.
+            return new ContextualSuggestionCardViewHolder(mRecyclerView, null, mUiDelegate,
+                    mUiConfig, OfflinePageBridge.getForProfile(mProfile));
+        }
+
+        @Override
+        public void onBindViewHolder(
+                ContextualSuggestionCardViewHolder holder, SnippetArticle item) {
+            holder.onBindViewHolder(item, mCategoryInfo);
+        }
+    }
+
+    private final Profile mProfile;
+    private final UiConfig mUiConfig;
+    private final SuggestionsUiDelegate mUiDelegate;
+    private final SuggestionsCategoryInfo mCategoryInfo;
+
+    private SuggestionsRecyclerView mRecyclerView;
+
+    /**
+     * Construct a new {@link ContextualSuggestionsAdapter}.
+     * @param context The {@link Context} used to retrieve resources.
+     * @param profile The regular {@link Profile}.
+     * @param uiConfig The {@link UiConfig} used to adjust view display.
+     * @param uiDelegate The {@link SuggestionsUiDelegate} used to help construct items in the
+     *                   content view.
+     * @param model The {@link ContextualSuggestionsModel} for the component.
+     */
+    ContextualSuggestionsAdapter(Context context, Profile profile, UiConfig uiConfig,
+            SuggestionsUiDelegate uiDelegate, ContextualSuggestionsModel model) {
+        super(model);
+
+        setViewBinder(new ContextualSuggestionsViewBinder());
+
+        mProfile = profile;
+        mUiConfig = uiConfig;
+        mUiDelegate = uiDelegate;
+
+        mCategoryInfo = new SuggestionsCategoryInfo(KnownCategories.CONTEXTUAL,
+                context.getString(R.string.contextual_suggestions_title),
+                ContentSuggestionsCardLayout.FULL_CARD, ContentSuggestionsAdditionalAction.NONE,
+                false, "");
+    }
+
+    @Override
+    @ItemViewType
+    public int getItemViewType(int position) {
+        return ItemViewType.SNIPPET;
+    }
+
+    @Override
+    public void onAttachedToRecyclerView(RecyclerView recyclerView) {
+        mRecyclerView = (SuggestionsRecyclerView) recyclerView;
+    }
+
+    @Override
+    public void onDetachedFromRecyclerView(RecyclerView recyclerView) {
+        mRecyclerView = null;
+    }
+
+    @Override
+    public void onViewRecycled(ContextualSuggestionCardViewHolder holder) {
+        holder.recycle();
+    }
+}

chrome/android/java/src/org/chromium/chrome/browser/contextualsuggestions/ContextualSuggestionsBottomSheetContent.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.contextualsuggestions;
+
+import android.view.View;
+
+import org.chromium.chrome.browser.widget.bottomsheet.BottomSheet.BottomSheetContent;
+
+/** A {@link BottomSheetContent} that displays contextual suggestions. */
+public class ContextualSuggestionsBottomSheetContent implements BottomSheetContent {
+    private ContentCoordinator mContentCoordinator;
+
+    /**
+     * Construct a new {@link ContextualSuggestionsBottomSheetContent}.
+     * @param contentCoordinator The {@link ContentCoordinator} that manages content to be
+     *                           displayed.
+     */
+    ContextualSuggestionsBottomSheetContent(ContentCoordinator contentCoordinator) {
+        mContentCoordinator = contentCoordinator;
+    }
+
+    @Override
+    public View getContentView() {
+        return mContentCoordinator.getView();
+    }
+
+    @Override
+    public View getToolbarView() {
+        return null;
+    }
+
+    @Override
+    public int getVerticalScrollOffset() {
+        return mContentCoordinator.getVerticalScrollOffset();
+    }
+
+    @Override
+    public void destroy() {
+        mContentCoordinator = null;
+    }
+
+    @Override
+    public boolean applyDefaultTopPadding() {
+        return false;
+    }
+}

chrome/android/java/src/org/chromium/chrome/browser/contextualsuggestions/ContextualSuggestionsCoordinator.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.contextualsuggestions;
+
+import org.chromium.chrome.browser.ChromeActivity;
+import org.chromium.chrome.browser.ntp.snippets.SuggestionsSource;
+import org.chromium.chrome.browser.profiles.Profile;
+import org.chromium.chrome.browser.suggestions.SuggestionsNavigationDelegate;
+import org.chromium.chrome.browser.suggestions.SuggestionsNavigationDelegateImpl;
+import org.chromium.chrome.browser.suggestions.SuggestionsUiDelegateImpl;
+import org.chromium.chrome.browser.tabmodel.TabModelSelector;
+import org.chromium.chrome.browser.widget.bottomsheet.BottomSheet;
+
+/**
+ * The coordinator for the contextual suggestions UI component. Manages communication with other
+ * parts of the UI-layer and lifecycle of shared component objects.
+ *
+ * This parent coordinator manages two sub-components, controlled by {@link ContentCoordinator}
+ * and {@link ToolbarCoordinator}. These sub-components each have their own views and view binders.
+ * They share a {@link ContextualSuggestionsMediator} and {@link ContextualSuggestionsModel}.
+ */
+public class ContextualSuggestionsCoordinator {
+    private ChromeActivity mActivity;
+    private BottomSheet mBottomSheet;
+    private Profile mProfile;
+
+    private ContextualSuggestionsModel mModel;
+    private ContextualSuggestionsMediator mMediator;
+    private ContentCoordinator mContentCoordinator;
+
+    private SuggestionsUiDelegateImpl mUiDelegate;
+
+    private ContextualSuggestionsBottomSheetContent mBottomSheetContent;
+
+    /**
+     * Construct a new {@link ContextualSuggestionsCoordinator}.
+     * @param activity The containing {@link ChromeActivity}.
+     * @param bottomSheet The {@link BottomSheet} where contextual suggestions will be displayed.
+     * @param tabModelSelector The {@link TabModelSelector} for the activity.
+     */
+    public ContextualSuggestionsCoordinator(
+            ChromeActivity activity, BottomSheet bottomSheet, TabModelSelector tabModelSelector) {
+        mActivity = activity;
+        mBottomSheet = bottomSheet;
+        mProfile = Profile.getLastUsedProfile().getOriginalProfile();
+
+        mModel = new ContextualSuggestionsModel();
+        mMediator = new ContextualSuggestionsMediator(mProfile, tabModelSelector, this, mModel);
+
+        SuggestionsSource suggestionsSource = mMediator.getSuggestionsSource();
+        SuggestionsNavigationDelegate navigationDelegate = new SuggestionsNavigationDelegateImpl(
+                mActivity, mProfile, mBottomSheet, tabModelSelector);
+        mUiDelegate = new SuggestionsUiDelegateImpl(suggestionsSource, new DummyEventReporter(),
+                navigationDelegate, mProfile, mBottomSheet,
+                mActivity.getChromeApplication().getReferencePool(),
+                mActivity.getSnackbarManager());
+    }
+
+    /** Called when the containing activity is destroyed. */
+    public void destroy() {
+        mMediator.destroy();
+
+        if (mContentCoordinator != null) mContentCoordinator.destroy();
+        if (mBottomSheetContent != null) mBottomSheetContent.destroy();
+    }
+
+    /**
+     * Displays contextual suggestions in the {@link BottomSheet}.
+     */
+    void displaySuggestions() {
+        // TODO(twellington): Introduce another method that creates bottom sheet content with only
+        // a toolbar view when suggestions are fist available, and use this method to construct the
+        // content view when the sheet is opened.
+        mContentCoordinator =
+                new ContentCoordinator(mActivity, mBottomSheet, mProfile, mUiDelegate, mModel);
+        mBottomSheetContent = new ContextualSuggestionsBottomSheetContent(mContentCoordinator);
+        mBottomSheet.showContent(mBottomSheetContent);
+    }
+
+    /** Removes contextual suggestions from the {@link BottomSheet}. */
+    void removeSuggestions() {
+        if (mContentCoordinator != null) {
+            mContentCoordinator.destroy();
+            mContentCoordinator = null;
+        }
+
+        if (mBottomSheetContent == null) return;
+
+        mBottomSheet.showContent(null);
+
+        mBottomSheetContent.destroy();
+        mBottomSheetContent = null;
+    }
+}

chrome/android/java/src/org/chromium/chrome/browser/contextualsuggestions/ContextualSuggestionsMediator.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.contextualsuggestions;
+
+import android.support.annotation.Nullable;
+import android.text.TextUtils;
+import android.webkit.URLUtil;
+
+import org.chromium.base.ContextUtils;
+import org.chromium.chrome.browser.ntp.snippets.SnippetArticle;
+import org.chromium.chrome.browser.ntp.snippets.SnippetsBridge;
+import org.chromium.chrome.browser.ntp.snippets.SuggestionsSource;
+import org.chromium.chrome.browser.profiles.Profile;
+import org.chromium.chrome.browser.tab.EmptyTabObserver;
+import org.chromium.chrome.browser.tab.Tab;
+import org.chromium.chrome.browser.tab.TabObserver;
+import org.chromium.chrome.browser.tabmodel.TabModel.TabSelectionType;
+import org.chromium.chrome.browser.tabmodel.TabModelSelector;
+import org.chromium.chrome.browser.tabmodel.TabModelSelectorTabModelObserver;
+import org.chromium.chrome.browser.util.UrlUtilities;
+import org.chromium.ui.widget.Toast;
+
+import java.util.ArrayList;
+
+/**
+ * A mediator for the contextual suggestions UI component responsible for interacting with
+ * the contextual suggestions backend, updating the model, and communicating with the
+ * component coordinator(s).
+ */
+class ContextualSuggestionsMediator {
+    private ContextualSuggestionsCoordinator mCoordinator;
+    private ContextualSuggestionsModel mModel;
+
+    private SnippetsBridge mBridge;
+
+    private final TabModelSelectorTabModelObserver mTabModelObserver;
+    private final TabObserver mTabObserver;
+    private Tab mLastTab;
+
+    @Nullable
+    private String mCurrentContextUrl;
+
+    /**
+     * Construct a new {@link ContextualSuggestionsMediator}.
+     * @param profile The regular {@link Profile}.
+     * @param tabModelSelector The {@link TabModelSelector} for the containing activity.
+     * @param coordinator The {@link ContextualSuggestionsCoordinator} for the component.
+     * @param model The {@link ContextualSuggestionsModel} for the component.
+     */
+    ContextualSuggestionsMediator(Profile profile, TabModelSelector tabModelSelector,
+            ContextualSuggestionsCoordinator coordinator, ContextualSuggestionsModel model) {
+        mCoordinator = coordinator;
+        mModel = model;
+
+        mBridge = new SnippetsBridge(Profile.getLastUsedProfile());
+
+        // TODO(twellington): Remove the following code for tab observing after triggering logic
+        // moves to the C++ layer.
+        mTabObserver = new EmptyTabObserver() {
+            @Override
+            public void onUpdateUrl(Tab tab, String url) {
+                refresh(url);
+            }
+        };
+
+        mTabModelObserver = new TabModelSelectorTabModelObserver(tabModelSelector) {
+            @Override
+            public void didSelectTab(Tab tab, TabSelectionType type, int lastId) {
+                updateCurrentTab(tab);
+            }
+        };
+
+        updateCurrentTab(tabModelSelector.getCurrentTab());
+    }
+
+    /**
+     * @return The {@link SuggestionsSource} used to fetch suggestions.
+     *
+     * TODO(twellington): This method is needed to construct {@link SuggestionsUiDelegateImpl} in
+     * the coordinator. Try to remove this dependency.
+     */
+    SuggestionsSource getSuggestionsSource() {
+        return mBridge;
+    }
+
+    /** Destroys the mediator. */
+    void destroy() {
+        if (mLastTab != null) {
+            mLastTab.removeObserver(mTabObserver);
+            mLastTab = null;
+        }
+        mTabModelObserver.destroy();
+    }
+
+    // TODO(twellington): Remove this method after triggering logic moves to the C++ layer.
+    private void refresh(@Nullable final String newUrl) {
+        if (!URLUtil.isNetworkUrl(newUrl)) {
+            clearSuggestions();
+            return;
+        }
+
+        // Do nothing if there are already suggestions in the suggestions list for the new context.
+        if (isContextTheSame(newUrl)) return;
+
+        // Context has changed, so we want to remove any old suggestions from the section.
+        clearSuggestions();
+        mCurrentContextUrl = newUrl;
+
+        Toast.makeText(ContextUtils.getApplicationContext(), "Fetching suggestions...",
+                     Toast.LENGTH_SHORT)
+                .show();
+
+        mBridge.fetchContextualSuggestions(newUrl, (suggestions) -> {
+            // Avoiding double fetches causing suggestions for incorrect context.
+            if (!TextUtils.equals(newUrl, mCurrentContextUrl)) return;
+
+            Toast.makeText(ContextUtils.getApplicationContext(),
+                         suggestions.size() + " suggestions fetched", Toast.LENGTH_SHORT)
+                    .show();
+
+            if (suggestions.size() > 0) {
+                mModel.setSuggestions(suggestions);
+                mCoordinator.displaySuggestions();
+            };
+        });
+    }
+
+    private void clearSuggestions() {
+        mModel.setSuggestions(new ArrayList<SnippetArticle>());
+        mCoordinator.removeSuggestions();
+    }
+
+    private boolean isContextTheSame(String newUrl) {
+        return UrlUtilities.urlsMatchIgnoringFragments(newUrl, mCurrentContextUrl);
+    }
+
+    /**
+     * Update the current tab and refresh suggestions.
+     * @param tab The current {@link Tab}.
+     */
+    private void updateCurrentTab(Tab tab) {
+        if (mLastTab != null) mLastTab.removeObserver(mTabObserver);
+
+        mLastTab = tab;
+        if (mLastTab == null) return;
+
+        mLastTab.addObserver(mTabObserver);
+        refresh(mLastTab.getUrl());
+    }
+}

chrome/android/java/src/org/chromium/chrome/browser/contextualsuggestions/ContextualSuggestionsModel.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.contextualsuggestions;
+
+import org.chromium.chrome.browser.modelutil.ListObservable;
+import org.chromium.chrome.browser.ntp.snippets.SnippetArticle;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/** A model for the contextual suggestions UI component. */
+class ContextualSuggestionsModel extends ListObservable<SnippetArticle> {
+    private List<SnippetArticle> mSuggestions = new ArrayList<>();
+
+    /**
+     * @param suggestions The list of current suggestions. May be an empty list if no
+     *                    suggestions are available.
+     */
+    void setSuggestions(List<SnippetArticle> suggestions) {
+        assert suggestions != null;
+
+        if (suggestions.size() == 0 && mSuggestions.size() == 0) return;
+
+        int oldLength = getItemCount();
+        mSuggestions = suggestions;
+
+        if (oldLength != 0) notifyItemRangeRemoved(0, oldLength);
+        if (mSuggestions.size() != 0) {
+            notifyItemRangeInserted(0, mSuggestions.size());
+        }
+    }
+
+    /** @return The list of current suggestions. */
+    List<SnippetArticle> getSuggestions() {
+        return mSuggestions;
+    }
+
+    @Override
+    public int getItemCount() {
+        return mSuggestions.size();
+    }
+
+    @Override
+    public SnippetArticle getItem(int position) {
+        assert position < mSuggestions.size();
+
+        return mSuggestions.get(position);
+    }
+}

chrome/android/java/src/org/chromium/chrome/browser/contextualsuggestions/DummyEventReporter.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.contextualsuggestions;
+
+import org.chromium.chrome.browser.ntp.cards.ActionItem;
+import org.chromium.chrome.browser.ntp.snippets.SnippetArticle;
+import org.chromium.chrome.browser.suggestions.SuggestionsEventReporter;
+import org.chromium.chrome.browser.suggestions.SuggestionsRanker;
+
+/** A dummy {@link SuggestionsEventReporter} to use until a real one replaces it. */
+class DummyEventReporter implements SuggestionsEventReporter {
+    @Override
+    public void onSurfaceOpened() {}
+
+    @Override
+    public void onPageShown(
+            int[] categories, int[] suggestionsPerCategory, boolean[] isCategoryVisible) {}
+
+    @Override
+    public void onSuggestionShown(SnippetArticle suggestion) {}
+
+    @Override
+    public void onSuggestionOpened(SnippetArticle suggestion, int windowOpenDisposition,
+            SuggestionsRanker suggestionsRanker) {}
+
+    @Override
+    public void onSuggestionMenuOpened(SnippetArticle suggestion) {}
+
+    @Override
+    public void onMoreButtonShown(ActionItem category) {}
+
+    @Override
+    public void onMoreButtonClicked(ActionItem category) {}
+}
\ No newline at end of file

chrome/android/java/src/org/chromium/chrome/browser/contextualsuggestions/OWNERS

+file://chrome/android/java/src/org/chromium/chrome/browser/ntp/OWNERS
+
+twellington@chromium.org
\ No newline at end of file

chrome/android/java/src/org/chromium/chrome/browser/modelutil/ListObservable.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 org.chromium.base.ObserverList;
+
+/**
+ * A base class for models maintaining a list of items. Note that ListObservable models do not need
+ * to be implemented as a list. Internally they may use any structure to organize their items.
+ *
+ * @param <E> The type of items held by the model.
+ */
+public abstract class ListObservable<E> {
+    /**
+     * An observer to be notified of changes to a {@link ListObservable}.
+     *
+     * @param <E> The type of items held by the observed model.
+     */
+    public interface ListObserver<E> {
+        /**
+         * Notifies that {@code count} items starting at position {@code index} under the
+         * {@code source} have been added.
+         *
+         * @param source The list to which items have been added.
+         * @param index The starting position of the range of added items.
+         * @param count The number of added items.
+         */
+        void onItemRangeInserted(ListObservable<E> source, int index, int count);
+
+        /**
+         * Notifies that {@code count} items starting at position {@code index} under the
+         * {@code source} have been removed.
+         *
+         * @param source The list from which items have been removed.
+         * @param index The starting position of the range of removed items.
+         * @param count The number of removed items.
+         */
+        void onItemRangeRemoved(ListObservable<E> source, int index, int count);
+
+        /**
+         * Notifies that {@code count} items starting at position {@code index} under the
+         * {@code source} have changed, with an optional payload object.
+         *
+         * @param source The list whose items have changed.
+         * @param index The starting position of the range of changed items.
+         * @param count The number of changed items.
+         * @param payload Optional parameter, use {@code null} to identify a "full" update.
+         */
+        void onItemRangeChanged(
+                ListObservable<E> source, int index, int count, @Nullable Object payload);
+    }
+
+    private final ObserverList<ListObserver<E>> mObservers = new ObserverList<>();
+
+    /** @return The total number of items held by the model. */
+    public abstract int getItemCount();
+
+    /**
+     * Retrieve the item at the specified {@code position}.
+     *
+     * @param position The position of the item to retrieve.
+     * @return The item at the specified {@code position}.
+     */
+    public abstract E getItem(int position);
+
+    /**
+     * @param observer An observer to be notified of changes to the model.
+     */
+    public void addObserver(ListObserver<E> observer) {
+        mObservers.addObserver(observer);
+    }
+
+    /** @param observer The observer to remove. */
+    public void removeObserver(ListObserver<E> observer) {
+        mObservers.removeObserver(observer);
+    }
+
+    /**
+     * Notifies observers that {@code count} items starting at position {@code index} have been
+     * added.
+     *
+     * @param index The starting position of the range of added items.
+     * @param count The number of added items.
+     */
+    protected void notifyItemRangeInserted(int index, int count) {
+        for (ListObserver<E> observer : mObservers) {
+            observer.onItemRangeInserted(this, index, count);
+        }
+    }
+
+    /**
+     * Notifies observes that {@code count} items starting at position {@code index} have been
+     * removed.
+     *
+     * @param index The starting position of the range of removed items.
+     * @param count The number of removed items.
+     */
+    protected void notifyItemRangeRemoved(int index, int count) {
+        for (ListObserver<E> observer : mObservers) {
+            observer.onItemRangeRemoved(this, index, count);
+        }
+    }
+
+    /**
+     * Notifies observers that {@code count} items starting at position {@code index} under the
+     * {@code source} have changed, with an optional payload object.
+     *
+     * @param index The starting position of the range of changed items.
+     * @param count The number of changed items.
+     * @param payload Optional parameter, use {@code null} to identify a "full" update.
+     */
+    protected void notifyItemRangeChanged(int index, int count, @Nullable Object payload) {
+        for (ListObserver<E> observer : mObservers) {
+            observer.onItemRangeChanged(this, index, count, payload);
+        }
+    }
+}

chrome/android/java/src/org/chromium/chrome/browser/modelutil/OWNERS

+bauerb@chromium.org
+twellington@chromium.org
\ No newline at end of file

chrome/android/java/src/org/chromium/chrome/browser/modelutil/RecyclerViewAdapter.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.v7.widget.RecyclerView;
+import android.support.v7.widget.RecyclerView.ViewHolder;
+import android.view.ViewGroup;
+
+/**
+ * An adapter that uses a {@link ViewBinder} to bind items in a {@link ListObservable} model to
+ * {@link ViewHolder}s.
+ *
+ * @param <E> The type of items held by the {@link ListObservable} model.
+ * @param <VH> The {@link ViewHolder} type for the {@link RecyclerView}.
+ */
+public class RecyclerViewAdapter<E, VH extends ViewHolder> extends RecyclerView.Adapter<VH> {
+    /**
+     * A view binder used to bind items in the {@link ListObservable} model to {@link ViewHolder}s.
+     *
+     * @param <E> The type of items held by the {@link ListObservable} model.
+     * @param <VH> The {@link ViewHolder} type for the {@link RecyclerView}.
+     */
+    public interface ViewBinder<E, VH> {
+        /**
+         * Called when the {@link RecyclerView} needs a new {@link ViewHolder} of the given
+         * {@code viewType} to represent an item.
+         *
+         * @param parent The {@link ViewGroup} into which the new {@link View} will be added after
+         *               it's bound to an adapter position.
+         * @param viewType The view type of the new {@link View}.
+         * @return A new {@link ViewHolder} that holds a {@link View} of the given view type.
+         */
+        VH onCreateViewHolder(ViewGroup parent, int viewType);
+
+        /**
+         * Called to display the {@code item} in the provided {@code holder}.
+         *
+         * @param holder The {@link ViewHolder} which should be updated to represent {@code item}.
+         * @param item The item to be bound.
+         */
+        void onBindViewHolder(VH holder, E item);
+    }
+
+    protected final ListObservable<E> mModel;
+
+    private ViewBinder<E, VH> mViewBinder;
+
+    /**
+     * Construct a new {@link RecyclerViewAdapter}.
+     * @param model The {@link ListObservable} model used to retrieve items to display in the
+     *              {@link RecyclerView}.
+     */
+    public RecyclerViewAdapter(ListObservable<E> model) {
+        mModel = model;
+    }
+
+    /**
+     * Set the {@link ViewBinder} to use with this adapter.
+     *
+     * @param viewBinder The {@link ViewBinder} used to bind items in the {@link ListObservable}
+     *                   model to {@link ViewHolder}s.
+     */
+    public void setViewBinder(ViewBinder<E, VH> viewBinder) {
+        mViewBinder = viewBinder;
+    }
+
+    @Override
+    public int getItemCount() {
+        return mModel.getItemCount();
+    }
+
+    @Override
+    public VH onCreateViewHolder(ViewGroup parent, int viewType) {
+        return mViewBinder.onCreateViewHolder(parent, viewType);
+    }
+
+    @Override
+    public void onBindViewHolder(VH holder, int position) {
+        mViewBinder.onBindViewHolder(holder, mModel.getItem(position));
+    }
+}

chrome/android/java/src/org/chromium/chrome/browser/modelutil/RecyclerViewModelChangeProcessor.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.v7.widget.RecyclerView;
+import android.support.v7.widget.RecyclerView.ViewHolder;
+
+import org.chromium.chrome.browser.modelutil.ListObservable.ListObserver;
+
+/**
+ * A model change processor for use with a {@link RecyclerView}. The
+ * {@link RecyclerViewModelChangeProcessor} should be registered as an observer of a
+ * {@link ListObservable} model. Notifies the associated {@link RecyclerViewAdapter<E, VH>} of
+ * changes to the model.
+ *
+ * @param <E> The type of items held by the {@link ListObservable} model.
+ * @param <VH> The {@link ViewHolder} type for the RecyclerView.
+ */
+public class RecyclerViewModelChangeProcessor<E, VH extends ViewHolder> implements ListObserver<E> {
+    private RecyclerViewAdapter<E, VH> mAdapter;
+
+    /**
+     * Constructs a new {@link RecyclerViewModelChangeProcessor}.
+     * @param adapter The {@link RecyclerViewAdapter<E, VH>} to be notified of changes to a
+     *                {@link ListObservable} model.
+     */
+    public RecyclerViewModelChangeProcessor(RecyclerViewAdapter<E, VH> adapter) {
+        mAdapter = adapter;
+    }
+
+    @Override
+    public void onItemRangeInserted(ListObservable<E> source, int index, int count) {
+        mAdapter.notifyItemRangeInserted(index, count);
+    }
+
+    @Override
+    public void onItemRangeRemoved(ListObservable<E> source, int index, int count) {
+        mAdapter.notifyItemRangeRemoved(index, count);
+    }
+
+    @Override
+    public void onItemRangeChanged(ListObservable<E> source, int index, int count, Object payload) {
+        mAdapter.notifyItemRangeChanged(index, count, payload);
+    }
+}

chrome/android/java_sources.gni

@@ -289,6 +289,14 @@ chrome_java_sources = [
   "java/src/org/chromium/chrome/browser/contextualsearch/TapSuppressionHeuristics.java",
   "java/src/org/chromium/chrome/browser/contextualsearch/TapWordEdgeSuppression.java",
   "java/src/org/chromium/chrome/browser/contextualsearch/TapWordLengthSuppression.java",
+  "java/src/org/chromium/chrome/browser/contextualsuggestions/ContentCoordinator.java",
+  "java/src/org/chromium/chrome/browser/contextualsuggestions/ContextualSuggestionsAdapter.java",
+  "java/src/org/chromium/chrome/browser/contextualsuggestions/ContextualSuggestionsBottomSheetContent.java",
+  "java/src/org/chromium/chrome/browser/contextualsuggestions/ContextualSuggestionCardViewHolder.java",
+  "java/src/org/chromium/chrome/browser/contextualsuggestions/ContextualSuggestionsCoordinator.java",
+  "java/src/org/chromium/chrome/browser/contextualsuggestions/ContextualSuggestionsMediator.java",
+  "java/src/org/chromium/chrome/browser/contextualsuggestions/ContextualSuggestionsModel.java",
+  "java/src/org/chromium/chrome/browser/contextualsuggestions/DummyEventReporter.java",
   "java/src/org/chromium/chrome/browser/cookies/CanonicalCookie.java",
   "java/src/org/chromium/chrome/browser/cookies/CookiesFetcher.java",
   "java/src/org/chromium/chrome/browser/coordinator/CoordinatorLayoutForPointer.java",
@@ -651,6 +659,9 @@ chrome_java_sources = [
   "java/src/org/chromium/chrome/browser/modaldialog/ModalDialogView.java",
   "java/src/org/chromium/chrome/browser/modaldialog/TabModalLifetimeHandler.java",
   "java/src/org/chromium/chrome/browser/modaldialog/TabModalPresenter.java",
+  "java/src/org/chromium/chrome/browser/modelutil/ListObservable.java",
+  "java/src/org/chromium/chrome/browser/modelutil/RecyclerViewModelChangeProcessor.java",
+  "java/src/org/chromium/chrome/browser/modelutil/RecyclerViewAdapter.java",
   "java/src/org/chromium/chrome/browser/mojo/ChromeInterfaceRegistrar.java",
   "java/src/org/chromium/chrome/browser/multiwindow/MultiInstanceChromeTabbedActivity.java",
   "java/src/org/chromium/chrome/browser/multiwindow/MultiWindowUtils.java",