[Tab View] Add TabViewManager and TabViewProvider

This CL implements a new system for managing custom Views for Tab.
The TabViewManager class acts as the entry point for all users who want
to display a View on top of Tab's Content view.

TabViewManager knows the priority of all its users and always displays
the TabViewProvider with the highest priority.

Internal design doc: http://go/tab-view-clients

Bug: 1073948
Change-Id: I5d5d0384b512d6722dd0357295de5542b9b77306
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2159248Reviewed-by: Theresa  <twellington@chromium.org>
Reviewed-by: Patrick Noland <pnoland@chromium.org>
Reviewed-by: Mehran Mahmoudi <mahmoudi@chromium.org>
Reviewed-by: Jinsuk Kim <jinsukkim@chromium.org>
Commit-Queue: Mehran Mahmoudi <mahmoudi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#763351}

chrome/android/chrome_java_sources.gni

@@ -1598,6 +1598,8 @@ chrome_java_sources = [
   "java/src/org/chromium/chrome/browser/tab/TabUma.java",
   "java/src/org/chromium/chrome/browser/tab/TabUtils.java",
   "java/src/org/chromium/chrome/browser/tab/TabViewAndroidDelegate.java",
+  "java/src/org/chromium/chrome/browser/tab/TabViewManager.java",
+  "java/src/org/chromium/chrome/browser/tab/TabViewProvider.java",
   "java/src/org/chromium/chrome/browser/tab/TabWebContentsDelegateAndroid.java",
   "java/src/org/chromium/chrome/browser/tab/TabWebContentsObserver.java",
   "java/src/org/chromium/chrome/browser/tab/TabWebContentsUserData.java",

chrome/android/chrome_junit_test_java_sources.gni

@@ -211,6 +211,7 @@ chrome_junit_test_java_sources = [
   "junit/src/org/chromium/chrome/browser/tab/TabBrowserControlsOffsetHelperTest.java",
   "junit/src/org/chromium/chrome/browser/tab/TabUnitTest.java",
   "junit/src/org/chromium/chrome/browser/tab/TabViewAndroidDelegateTest.java",
+  "junit/src/org/chromium/chrome/browser/tab/TabViewManagerTest.java",
   "junit/src/org/chromium/chrome/browser/tabmodel/TabModelSelectorImplTest.java",
   "junit/src/org/chromium/chrome/browser/tabmodel/TabModelSelectorProfileSupplierTest.java",
   "junit/src/org/chromium/chrome/browser/tabstate/TabStateUnitTest.java",

chrome/android/java/src/org/chromium/chrome/browser/compositor/layouts/content/TabContentManager.java

@@ -34,12 +34,11 @@ import org.chromium.chrome.R;
 import org.chromium.chrome.browser.flags.BooleanCachedFieldTrialParameter;
 import org.chromium.chrome.browser.flags.ChromeFeatureList;
 import org.chromium.chrome.browser.flags.ChromeSwitches;
-import org.chromium.chrome.browser.tab.SadTab;
 import org.chromium.chrome.browser.tab.Tab;
+import org.chromium.chrome.browser.tab.TabViewManager;
 import org.chromium.chrome.browser.tasks.tab_management.TabUiFeatureUtilities;
 import org.chromium.chrome.browser.ui.native_page.FrozenNativePage;
 import org.chromium.chrome.browser.ui.native_page.NativePage;
-import org.chromium.chrome.browser.usage_stats.SuspendedTab;
 import org.chromium.ui.base.DeviceFormFactor;
 import org.chromium.ui.display.DisplayAndroid;
 
@@ -280,7 +279,7 @@ public class TabContentManager {
 
         View viewToDraw = null;
         if (isNativeViewShowing) {
-            viewToDraw = tab.getContentView();
+            viewToDraw = tab.getView();
         } else if (!(nativePage instanceof FrozenNativePage)) {
             viewToDraw = nativePage.getView();
         }
@@ -644,7 +643,7 @@ public class TabContentManager {
     }
 
     private boolean isNativeViewShowing(Tab tab) {
-        return tab != null && (SadTab.isShowing(tab) || SuspendedTab.isShowing(tab));
+        return tab != null && TabViewManager.get(tab).getCurrentTabViewProvider() != null;
     }
 
     @NativeMethods

chrome/android/java/src/org/chromium/chrome/browser/paint_preview/PaintPreviewDemoManager.java

@@ -4,13 +4,16 @@
 
 package org.chromium.chrome.browser.paint_preview;
 
+import android.view.View;
+
 import org.chromium.base.task.PostTask;
 import org.chromium.chrome.R;
-import org.chromium.chrome.browser.lifecycle.Destroyable;
 import org.chromium.chrome.browser.paint_preview.services.PaintPreviewDemoService;
 import org.chromium.chrome.browser.paint_preview.services.PaintPreviewDemoServiceFactory;
 import org.chromium.chrome.browser.tab.Tab;
 import org.chromium.chrome.browser.tab.TabThemeColorHelper;
+import org.chromium.chrome.browser.tab.TabViewManager;
+import org.chromium.chrome.browser.tab.TabViewProvider;
 import org.chromium.components.paintpreview.player.PlayerManager;
 import org.chromium.content_public.browser.LoadUrlParams;
 import org.chromium.content_public.browser.UiThreadTaskTraits;
@@ -21,7 +24,7 @@ import org.chromium.url.GURL;
  * Responsible for displaying the Paint Preview demo. When displaying, the Paint Preview will
  * overlay the associated {@link Tab}'s content view.
  */
-public class PaintPreviewDemoManager implements Destroyable {
+public class PaintPreviewDemoManager implements TabViewProvider {
     private Tab mTab;
     private PaintPreviewDemoService mPaintPreviewDemoService;
     private PlayerManager mPlayerManager;
@@ -66,28 +69,22 @@ public class PaintPreviewDemoManager implements Destroyable {
                     .show();
             return;
         }
-        mTab.getContentView().addView(mPlayerManager.getView());
-        Toast.makeText(mTab.getContext(), R.string.paint_preview_demo_playback_start,
-                     Toast.LENGTH_LONG)
-                .show();
+        TabViewManager.get(mTab).addTabViewProvider(this);
     }
 
-    public void removePaintPreviewDemo() {
+    void removePaintPreviewDemo() {
         if (mTab == null || mPlayerManager == null) {
             return;
         }
 
-        mTab.getContentView().removeView(mPlayerManager.getView());
+        TabViewManager.get(mTab).removeTabViewProvider(this);
         mPaintPreviewDemoService.cleanUpForTabId(mTab.getId());
         mPlayerManager = null;
-        Toast.makeText(
-                     mTab.getContext(), R.string.paint_preview_demo_playback_end, Toast.LENGTH_LONG)
-                .show();
     }
 
-    public boolean isShowingPaintPreviewDemo() {
+    boolean isShowingPaintPreviewDemo() {
         return mPlayerManager != null
-                && mPlayerManager.getView().getParent() == mTab.getContentView();
+                && TabViewManager.get(mTab).getCurrentTabViewProvider() == this;
     }
 
     private void onLinkClicked(GURL url) {
@@ -96,10 +93,33 @@ public class PaintPreviewDemoManager implements Destroyable {
         mTab.loadUrl(new LoadUrlParams(url.getSpec()));
     }
 
-    @Override
     public void destroy() {
         if (mPaintPreviewDemoService != null) {
             mPaintPreviewDemoService.cleanUpForTabId(mTab.getId());
         }
     }
+
+    @Override
+    public int getTabViewProviderType() {
+        return Type.PAINT_PREVIEW;
+    }
+
+    @Override
+    public View getView() {
+        return mPlayerManager == null ? null : mPlayerManager.getView();
+    }
+
+    @Override
+    public void onShown() {
+        Toast.makeText(mTab.getContext(), R.string.paint_preview_demo_playback_start,
+                     Toast.LENGTH_LONG)
+                .show();
+    }
+
+    @Override
+    public void onHidden() {
+        Toast.makeText(
+                     mTab.getContext(), R.string.paint_preview_demo_playback_end, Toast.LENGTH_LONG)
+                .show();
+    }
 }

chrome/android/java/src/org/chromium/chrome/browser/tab/SadTab.java

@@ -12,9 +12,8 @@ import android.text.method.LinkMovementMethod;
 import android.view.LayoutInflater;
 import android.view.View;
 import android.view.View.OnClickListener;
+import android.view.ViewGroup.LayoutParams;
 import android.widget.Button;
-import android.widget.FrameLayout;
-import android.widget.FrameLayout.LayoutParams;
 import android.widget.TextView;
 
 import androidx.annotation.VisibleForTesting;
@@ -35,7 +34,7 @@ import org.chromium.ui.widget.ChromeBulletSpan;
  * Represent the sad tab displayed in place of a crashed renderer. Instantiated on the first
  * |show()| request from a Tab, and destroyed together with it.
  */
-public class SadTab extends EmptyTabObserver implements UserData {
+public class SadTab extends EmptyTabObserver implements UserData, TabViewProvider {
     private static final Class<SadTab> USER_DATA_KEY = SadTab.class;
 
     private final TabImpl mTab;
@@ -113,10 +112,7 @@ public class SadTab extends EmptyTabObserver implements UserData {
                 suggestionAction, buttonAction, showSendFeedbackView, mTab.isIncognito());
         mSadTabSuccessiveRefreshCounter++;
 
-        // Show the sad tab inside ContentView.
-        mTab.getContentView().addView(mView,
-                new FrameLayout.LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT));
-        mTab.notifyContentChanged();
+        TabViewManager.get(mTab).addTabViewProvider(this);
     }
 
     /**
@@ -124,10 +120,7 @@ public class SadTab extends EmptyTabObserver implements UserData {
      */
     @VisibleForTesting
     public void removeIfPresent() {
-        if (isShowing()) {
-            mTab.getContentView().removeView(mView);
-            mTab.notifyContentChanged();
-        }
+        TabViewManager.get(mTab).removeTabViewProvider(this);
         mView = null;
     }
 
@@ -135,7 +128,7 @@ public class SadTab extends EmptyTabObserver implements UserData {
      * @return Whether or not the sad tab is showing.
      */
     public boolean isShowing() {
-        return mView != null && mView.getParent() == mTab.getContentView();
+        return mView != null && TabViewManager.get(mTab).getCurrentTabViewProvider() == this;
     }
 
     // TabObserver
@@ -181,6 +174,8 @@ public class SadTab extends EmptyTabObserver implements UserData {
         LayoutInflater inflater =
                 (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
         View sadTabView = inflater.inflate(R.layout.sad_tab, null);
+        sadTabView.setLayoutParams(
+                new LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT));
 
         TextView titleText = (TextView) sadTabView.findViewById(R.id.sad_tab_title);
         int titleTextId =
@@ -299,4 +294,14 @@ public class SadTab extends EmptyTabObserver implements UserData {
     public static void initForTesting(Tab tab, SadTab sadTab) {
         tab.getUserDataHost().setUserData(USER_DATA_KEY, sadTab);
     }
+
+    @Override
+    public int getTabViewProviderType() {
+        return Type.SAD_TAB;
+    }
+
+    @Override
+    public View getView() {
+        return mView;
+    }
 }

chrome/android/java/src/org/chromium/chrome/browser/tab/TabImpl.java

@@ -90,6 +90,9 @@ public class TabImpl implements Tab, TabObscuringHandler.Observer {
     /** The parent view of the ContentView and the InfoBarContainer. */
     private ContentView mContentView;
 
+    /** The view provided by {@link TabViewManager} to be shown on top of Content view. */
+    private View mCustomView;
+
     /** A list of Tab observers.  These are used to broadcast Tab events to listeners. */
     private final ObserverList<TabObserver> mObservers = new ObserverList<>();
 
@@ -334,6 +337,14 @@ public class TabImpl implements Tab, TabObscuringHandler.Observer {
         }
     }
 
+    /**
+     * Sets a custom {@link View} for this {@link Tab} that replaces Content view.
+     */
+    void setCustomView(@Nullable View view) {
+        mCustomView = view;
+        notifyContentChanged();
+    }
+
     @Override
     public ContentView getContentView() {
         return mContentView;
@@ -341,7 +352,11 @@ public class TabImpl implements Tab, TabObscuringHandler.Observer {
 
     @Override
     public View getView() {
-        return mNativePage != null ? mNativePage.getView() : mContentView;
+        if (mCustomView != null) return mCustomView;
+
+        if (mNativePage != null) return mNativePage.getView();
+
+        return mContentView;
     }
 
     @Override
@@ -790,7 +805,7 @@ public class TabImpl implements Tab, TabObscuringHandler.Observer {
 
         WebContentsAccessibility wcax = getWebContentsAccessibility(getWebContents());
         if (wcax != null) {
-            boolean isWebContentObscured = isObscured || SadTab.isShowing(this);
+            boolean isWebContentObscured = isObscured || mCustomView != null;
             wcax.setObscuredByAnotherView(isWebContentObscured);
         }
     }

chrome/android/java/src/org/chromium/chrome/browser/tab/TabViewManager.java

+// Copyright 2020 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.tab;
+
+import android.util.SparseIntArray;
+import android.view.View;
+
+import androidx.annotation.Nullable;
+import androidx.annotation.VisibleForTesting;
+
+import org.chromium.base.UserData;
+
+import java.util.Comparator;
+import java.util.PriorityQueue;
+
+/**
+ * TODO(crbug.com/1074348) Make this an interface and move it to //chrome/browser/tab.
+ * This class is responsible for displaying custom {@link View}s on top of {@link Tab}'s Content
+ * view. Users that want to display a custom {@link View} should:
+ *     1. Implement {@link TabViewProvider}
+ *     2. Add an entry to {@link TabViewProvider.Type}
+ *     3. Add their {@link TabViewProvider.Type} to {@link #PRIORITIZED_TAB_VIEW_PROVIDER_TYPES}
+ *        with an appropriate priority. In order to find the right priority, please consider the
+ *        existing entries in the array and determine where the new feature fits relative to them.
+ *     4. Use {@link #addTabViewProvider} and {@link #removeTabViewProvider} to add and remove their
+ *        {@link TabViewProvider}
+ */
+public class TabViewManager implements UserData, Comparator<TabViewProvider> {
+    /**
+     * A prioritized list of all {@link TabViewProvider.Type}s, from most important to least
+     * important. The {@link TabViewProvider} with the highest priority will always be shown first,
+     * regardless of its insertion time relative to other {@link TabViewProvider}s.
+     */
+    @VisibleForTesting
+    @TabViewProvider.Type
+    static final int[] PRIORITIZED_TAB_VIEW_PROVIDER_TYPES = new int[] {
+        TabViewProvider.Type.SUSPENDED_TAB,
+        TabViewProvider.Type.PAINT_PREVIEW,
+        TabViewProvider.Type.SAD_TAB};
+
+    /**
+     * A lookup table for {@link #PRIORITIZED_TAB_VIEW_PROVIDER_TYPES}. This is initialized in the
+     * following static block and doesn't need to be manually updated.
+     */
+    private static final SparseIntArray TAB_VIEW_PROVIDER_PRIORITY_LOOKUP = new SparseIntArray();
+    static {
+        for (int i = 0; i < PRIORITIZED_TAB_VIEW_PROVIDER_TYPES.length; i++) {
+            TAB_VIEW_PROVIDER_PRIORITY_LOOKUP.put(PRIORITIZED_TAB_VIEW_PROVIDER_TYPES[i], i);
+        }
+    }
+    private static final Class<TabViewManager> USER_DATA_KEY = TabViewManager.class;
+
+    private PriorityQueue<TabViewProvider> mTabViewProviders;
+    private TabImpl mTab;
+
+    public static TabViewManager get(Tab tab) {
+        if (tab.getUserDataHost().getUserData(USER_DATA_KEY) == null) {
+            tab.getUserDataHost().setUserData(USER_DATA_KEY, new TabViewManager(tab));
+        }
+        return tab.getUserDataHost().getUserData(USER_DATA_KEY);
+    }
+
+    @VisibleForTesting
+    TabViewManager(Tab tab) {
+        mTab = (TabImpl) tab;
+        mTabViewProviders = new PriorityQueue<>(PRIORITIZED_TAB_VIEW_PROVIDER_TYPES.length, this);
+    }
+
+    /**
+     * @return The {@link TabViewProvider} that is being currently displayed.
+     */
+    public @Nullable TabViewProvider getCurrentTabViewProvider() {
+        return mTabViewProviders.peek();
+    }
+
+    /**
+     * Adds a {@link TabViewProvider} to be shown in the {@link Tab} associated with this {@link
+     * TabViewManager}. If the given {@link TabViewProvider} has the highest priority, it will be
+     * shown immediately. Otherwise, it will be shown after other {@link TabViewProvider}s with
+     * higher priorities are removed.
+     */
+    public void addTabViewProvider(TabViewProvider tabViewProvider) {
+        if (mTabViewProviders.contains(tabViewProvider)) return;
+
+        TabViewProvider currentTabViewProvider = mTabViewProviders.peek();
+        mTabViewProviders.add(tabViewProvider);
+        updateCurrentTabViewProvider(currentTabViewProvider);
+    }
+
+    /**
+     * Remove the given {@link TabViewProvider} from the {@link Tab} associated with this {@link
+     * TabViewManager}. If the given {@link TabViewProvider} is currently shown, the next available
+     * {@link TabViewProvider} with the highest priority will be shown. If there are no other {@link
+     * TabViewProvider}s, {@link Tab}'s Content view will be shown.
+     */
+    public void removeTabViewProvider(TabViewProvider tabViewProvider) {
+        TabViewProvider currentTabViewProvider = mTabViewProviders.peek();
+        mTabViewProviders.remove(tabViewProvider);
+        updateCurrentTabViewProvider(currentTabViewProvider);
+    }
+
+    private void updateCurrentTabViewProvider(TabViewProvider previousTabViewProvider) {
+        if (mTab == null) return;
+
+        TabViewProvider currentTabViewProvider = mTabViewProviders.peek();
+        if (currentTabViewProvider != previousTabViewProvider) {
+            View view = null;
+            if (currentTabViewProvider != null) {
+                view = currentTabViewProvider.getView();
+                assert view != null;
+            }
+            mTab.setCustomView(view);
+            if (previousTabViewProvider != null) previousTabViewProvider.onHidden();
+            if (currentTabViewProvider != null) currentTabViewProvider.onShown();
+        }
+    }
+
+    /**
+     * Compares two {@link TabViewProvider}s based on their priority in
+     * {@link #PRIORITIZED_TAB_VIEW_PROVIDER_TYPES}. Do not edit the logic here when you add a new
+     * {@link TabViewProvider.Type}. Instead, simply add your new {@link TabViewProvider.Type} to
+     * {@link #PRIORITIZED_TAB_VIEW_PROVIDER_TYPES}.
+     */
+    @Override
+    public int compare(TabViewProvider tvp1, TabViewProvider tvp2) {
+        int tvp1Priority = TAB_VIEW_PROVIDER_PRIORITY_LOOKUP.get(tvp1.getTabViewProviderType());
+        int tvp2Priority = TAB_VIEW_PROVIDER_PRIORITY_LOOKUP.get(tvp2.getTabViewProviderType());
+        return tvp1Priority - tvp2Priority;
+    }
+
+    @Override
+    public void destroy() {
+        mTab.setCustomView(null);
+        TabViewProvider currentTabViewProvider = mTabViewProviders.peek();
+        if (currentTabViewProvider != null) currentTabViewProvider.onHidden();
+        mTabViewProviders.clear();
+        mTab = null;
+    }
+}

chrome/android/java/src/org/chromium/chrome/browser/tab/TabViewProvider.java

+// Copyright 2020 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.tab;
+
+import android.view.View;
+
+import androidx.annotation.IntDef;
+
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+
+/**
+ * TODO(crbug.com/1074348) Move this interface to //chrome/browser/tab.
+ * An interface that provides a {@link View} to be shown in a {@link Tab}.
+ * Refer to the Javadoc on {@link TabViewManager} to learn how to add a new {@link TabViewProvider}
+ * to a {@link Tab}.
+ */
+public interface TabViewProvider {
+    /**
+     * Represents each {@link TabViewProvider} implementer. Please note that the integer values
+     * bear no ordering or prioritization meaning.
+     */
+    @IntDef({Type.SUSPENDED_TAB, Type.SAD_TAB, Type.PAINT_PREVIEW})
+    @Retention(RetentionPolicy.SOURCE)
+    @interface Type {
+        int SUSPENDED_TAB = 0;
+        int SAD_TAB = 1;
+        int PAINT_PREVIEW = 2;
+    }
+
+    /**
+     * @return The {@link Type} associated with this {@link TabViewProvider}.
+     */
+    @Type
+    int getTabViewProviderType();
+
+    /**
+     * @return The {@link View} that {@link Tab} is supposed to show.
+     */
+    View getView();
+
+    /**
+     * Called when the {@link View} provided by {@link #getView()} is provided to {@link Tab}.
+     * */
+    default void onShown() {}
+
+    /**
+     * Called when the {@link View} provided by {@link #getView()} is removed from {@link Tab}.
+     * */
+    default void onHidden() {}
+}

chrome/android/java/src/org/chromium/chrome/browser/tab/TabWebContentsObserver.java

@@ -206,7 +206,14 @@ public class TabWebContentsObserver extends TabWebContentsUserData {
                 }
             } else {
                 rendererCrashStatus = TAB_RENDERER_CRASH_STATUS_SHOWN_IN_FOREGROUND_APP;
-                SadTab.from(mTab).show();
+                // TODO(crbug.com/1074078): Remove the Handler and call SadTab directly when
+                // WebContentsObserverProxy observers' iterator concurrency issue is fixed.
+                // Showing the SadTab will cause the content view hosting WebContents to lose focus.
+                // Post the show in order to avoid immediately triggering
+                // {@link WebContentsObserver#onWebContentsLostFocus}. This will ensure all
+                // observers in {@link WebContentsObserverProxy} receive callbacks for
+                // {@link WebContentsObserver#renderProcessGone} first.
+                (new Handler()).post(SadTab.from(mTab)::show);
                 // This is necessary to correlate histogram data with stability counts.
                 RecordHistogram.recordBooleanHistogram("Stability.Android.RendererCrash", true);
             }

chrome/android/java/src/org/chromium/chrome/browser/usage_stats/SuspendedTab.java

@@ -10,9 +10,7 @@ import android.content.Intent;
 import android.view.LayoutInflater;
 import android.view.View;
 import android.view.View.OnClickListener;
-import android.view.ViewGroup;
-import android.widget.LinearLayout;
-import android.widget.LinearLayout.LayoutParams;
+import android.view.ViewGroup.LayoutParams;
 import android.widget.TextView;
 
 import androidx.annotation.Nullable;
@@ -28,6 +26,8 @@ import org.chromium.chrome.browser.media.MediaCaptureDevicesDispatcherAndroid;
 import org.chromium.chrome.browser.tab.EmptyTabObserver;
 import org.chromium.chrome.browser.tab.Tab;
 import org.chromium.chrome.browser.tab.TabImpl;
+import org.chromium.chrome.browser.tab.TabViewManager;
+import org.chromium.chrome.browser.tab.TabViewProvider;
 import org.chromium.content_public.browser.WebContents;
 import org.chromium.content_public.browser.WebContentsAccessibility;
 import org.chromium.ui.base.WindowAndroid;
@@ -36,7 +36,7 @@ import org.chromium.ui.base.WindowAndroid;
  * Represents the suspension page presented when a user tries to visit a site whose fully-qualified
  * domain name (FQDN) has been suspended via Digital Wellbeing.
  */
-public class SuspendedTab extends EmptyTabObserver implements UserData {
+public class SuspendedTab extends EmptyTabObserver implements UserData, TabViewProvider {
     private static final String DIGITAL_WELLBEING_SITE_DETAILS_ACTION =
             "org.chromium.chrome.browser.usage_stats.action.SHOW_WEBSITE_DETAILS";
     private static final String EXTRA_FQDN_NAME =
@@ -147,7 +147,7 @@ public class SuspendedTab extends EmptyTabObserver implements UserData {
 
     @VisibleForTesting
     boolean isViewAttached() {
-        return mView != null && mView.getParent() == mTab.getContentView();
+        return mView != null && TabViewManager.get(mTab).getCurrentTabViewProvider() == this;
     }
 
     private View createView() {
@@ -155,20 +155,16 @@ public class SuspendedTab extends EmptyTabObserver implements UserData {
         LayoutInflater inflater = LayoutInflater.from(context);
 
         View suspendedTabView = inflater.inflate(R.layout.suspended_tab, null);
+        suspendedTabView.setLayoutParams(
+                new LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT));
         return suspendedTabView;
     }
 
     private void attachView() {
         assert mView == null;
 
-        ViewGroup parent = mTab.getContentView();
-        // getContentView() will return null if the tab doesn't have a WebContents, which is
-        // possible in some situations, e.g. if the renderer crashes.
-        if (parent == null) return;
         mView = createView();
-        parent.addView(mView,
-                new LinearLayout.LayoutParams(
-                        LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT));
+        TabViewManager.get(mTab).addTabViewProvider(this);
         updateFqdnText();
     }
 
@@ -201,10 +197,8 @@ public class SuspendedTab extends EmptyTabObserver implements UserData {
     }
 
     private void removeViewIfPresent() {
-        if (isViewAttached()) {
-            mTab.getContentView().removeView(mView);
-            mView = null;
-        }
+        TabViewManager.get(mTab).removeTabViewProvider(this);
+        mView = null;
     }
 
     // TabObserver implementation.
@@ -222,4 +216,14 @@ public class SuspendedTab extends EmptyTabObserver implements UserData {
     public void destroy() {
         mTab.removeObserver(this);
     }
+
+    @Override
+    public int getTabViewProviderType() {
+        return Type.SUSPENDED_TAB;
+    }
+
+    @Override
+    public View getView() {
+        return mView;
+    }
 }

chrome/android/javatests/src/org/chromium/chrome/browser/tab/SadTabTest.java

@@ -4,6 +4,7 @@
 
 package org.chromium.chrome.browser.tab;
 
+import android.support.test.InstrumentationRegistry;
 import android.support.test.filters.SmallTest;
 import android.widget.Button;
 
@@ -44,6 +45,7 @@ public class SadTabTest {
     }
 
     private static boolean isShowingSadTab(Tab tab) {
+        InstrumentationRegistry.getInstrumentation().waitForIdleSync();
         try {
             return TestThreadUtils.runOnUiThreadBlocking(() -> SadTab.isShowing(tab));
         } catch (ExecutionException e) {
@@ -193,7 +195,12 @@ public class SadTabTest {
      *         doesn't exist.
      */
     private static Button getSadTabButton(Tab tab) {
-        return (Button) tab.getContentView().findViewById(R.id.sad_tab_button);
+        InstrumentationRegistry.getInstrumentation().waitForIdleSync();
+        try {
+            return TestThreadUtils.runOnUiThreadBlocking(
+                    () -> tab.getView().findViewById(R.id.sad_tab_button));
+        } catch (ExecutionException e) {
+            return null;
+        }
     }
-
 }

chrome/android/junit/src/org/chromium/chrome/browser/tab/TabViewManagerTest.java

+// Copyright 2020 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.tab;
+
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+import android.view.View;
+
+import org.junit.Assert;
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.Mock;
+import org.mockito.MockitoAnnotations;
+
+import org.chromium.base.test.BaseRobolectricTestRunner;
+
+/**
+ * Unit tests for the {@link TabViewManager} class.
+ */
+@RunWith(BaseRobolectricTestRunner.class)
+public class TabViewManagerTest {
+    @Mock
+    private TabImpl mTab;
+    @Mock
+    private TabViewProvider mTabViewProvider0;
+    @Mock
+    private TabViewProvider mTabViewProvider1;
+    @Mock
+    private TabViewProvider mTabViewProvider2;
+    @Mock
+    private View mTabView0;
+    @Mock
+    private View mTabView1;
+    @Mock
+    private View mTabView2;
+
+    private TabViewManager mTabViewManager;
+
+    @Before
+    public void setUp() {
+        MockitoAnnotations.initMocks(this);
+        mTabViewManager = new TabViewManager(mTab);
+        when(mTabViewProvider0.getTabViewProviderType())
+                .thenReturn(TabViewManager.PRIORITIZED_TAB_VIEW_PROVIDER_TYPES[0]);
+        when(mTabViewProvider1.getTabViewProviderType())
+                .thenReturn(TabViewManager.PRIORITIZED_TAB_VIEW_PROVIDER_TYPES[1]);
+        when(mTabViewProvider2.getTabViewProviderType())
+                .thenReturn(TabViewManager.PRIORITIZED_TAB_VIEW_PROVIDER_TYPES[2]);
+        when(mTabViewProvider0.getView()).thenReturn(mTabView0);
+        when(mTabViewProvider1.getView()).thenReturn(mTabView1);
+        when(mTabViewProvider2.getView()).thenReturn(mTabView2);
+    }
+
+    /**
+     * Verifies that the {@link TabViewProvider} with the highest priority is always
+     * showing after each call to {@link TabViewManager#addTabViewProvider}.
+     */
+    @Test
+    public void testAddTabViewProvider() {
+        mTabViewManager.addTabViewProvider(mTabViewProvider1);
+        Assert.assertEquals("TabViewProvider with the highest priority should be shown", mTabViewProvider1,
+                mTabViewManager.getCurrentTabViewProvider());
+        verify(mTab).setCustomView(mTabView1);
+        verifyTabViewProviderOnShownCalled(mTabViewProvider1, 1);
+        verifyTabViewProviderOnHiddenCalled(mTabViewProvider1, 0);
+
+        mTabViewManager.addTabViewProvider(mTabViewProvider2);
+        Assert.assertEquals("TabViewProvider with the highest priority should be shown", mTabViewProvider1,
+                mTabViewManager.getCurrentTabViewProvider());
+        verify(mTab).setCustomView(mTabView1);
+        verifyTabViewProviderOnShownCalled(mTabViewProvider1, 1);
+        verifyTabViewProviderOnShownCalled(mTabViewProvider2, 0);
+        verifyTabViewProviderOnHiddenCalled(mTabViewProvider1, 0);
+        verifyTabViewProviderOnHiddenCalled(mTabViewProvider2, 0);
+
+        mTabViewManager.addTabViewProvider(mTabViewProvider0);
+        Assert.assertEquals("TabViewProvider with the highest priority should be shown", mTabViewProvider0,
+                mTabViewManager.getCurrentTabViewProvider());
+        verify(mTab).setCustomView(mTabView0);
+        verifyTabViewProviderOnShownCalled(mTabViewProvider0, 1);
+        verifyTabViewProviderOnShownCalled(mTabViewProvider1, 1);
+        verifyTabViewProviderOnShownCalled(mTabViewProvider2, 0);
+        verifyTabViewProviderOnHiddenCalled(mTabViewProvider0, 0);
+        verifyTabViewProviderOnHiddenCalled(mTabViewProvider1, 1);
+        verifyTabViewProviderOnHiddenCalled(mTabViewProvider2, 0);
+    }
+
+    /**
+     * Verifies that the {@link TabViewProvider} with the highest priority is always
+     * showing after each call to {@link TabViewManager#removeTabViewProvider}.
+     */
+    @Test
+    public void testRemoveTabViewProvider() {
+        mTabViewManager.addTabViewProvider(mTabViewProvider0);
+        mTabViewManager.addTabViewProvider(mTabViewProvider2);
+        mTabViewManager.addTabViewProvider(mTabViewProvider1);
+        Assert.assertEquals("TabViewProvider with the highest priority should be shown", mTabViewProvider0,
+                mTabViewManager.getCurrentTabViewProvider());
+
+        mTabViewManager.removeTabViewProvider(mTabViewProvider0);
+        Assert.assertEquals("TabViewProvider with the highest priority should be shown", mTabViewProvider1,
+                mTabViewManager.getCurrentTabViewProvider());
+        verify(mTab).setCustomView(mTabView1);
+        verifyTabViewProviderOnShownCalled(mTabViewProvider0, 1);
+        verifyTabViewProviderOnShownCalled(mTabViewProvider1, 1);
+        verifyTabViewProviderOnShownCalled(mTabViewProvider2, 0);
+        verifyTabViewProviderOnHiddenCalled(mTabViewProvider0, 1);
+        verifyTabViewProviderOnHiddenCalled(mTabViewProvider1, 0);
+        verifyTabViewProviderOnHiddenCalled(mTabViewProvider2, 0);
+
+        mTabViewManager.removeTabViewProvider(mTabViewProvider2);
+        Assert.assertEquals("TabViewProvider with the highest priority should be shown", mTabViewProvider1,
+                mTabViewManager.getCurrentTabViewProvider());
+        verify(mTab).setCustomView(mTabView1);
+        verifyTabViewProviderOnShownCalled(mTabViewProvider1, 1);
+        verifyTabViewProviderOnShownCalled(mTabViewProvider2, 0);
+        verifyTabViewProviderOnHiddenCalled(mTabViewProvider1, 0);
+        verifyTabViewProviderOnHiddenCalled(mTabViewProvider2, 0);
+
+        mTabViewManager.removeTabViewProvider(mTabViewProvider1);
+        Assert.assertNull("No TabViewProvider should be shown", mTabViewManager.getCurrentTabViewProvider());
+        verify(mTab).setCustomView(null);
+        verifyTabViewProviderOnShownCalled(mTabViewProvider1, 1);
+        verifyTabViewProviderOnHiddenCalled(mTabViewProvider1, 1);
+    }
+
+    private void verifyTabViewProviderOnShownCalled(TabViewProvider mockTabViewProvider, int numberOfCalls) {
+        String description = "onShown() should have been called " + numberOfCalls + " times on TabViewProvider type "
+                + mockTabViewProvider.getTabViewProviderType();
+        verify(mockTabViewProvider, times(numberOfCalls).description(description)).onShown();
+    }
+
+    private void verifyTabViewProviderOnHiddenCalled(TabViewProvider mockTabViewProvider, int numberOfCalls) {
+        String description = "onHidden() should have been called " + numberOfCalls + " times on TabViewProvider type "
+                + mockTabViewProvider.getTabViewProviderType();
+        verify(mockTabViewProvider, times(numberOfCalls).description(description)).onHidden();
+    }
+}

chrome/android/junit/src/org/chromium/chrome/browser/usage_stats/PageViewObserverTest.java

@@ -26,6 +26,7 @@ import org.mockito.ArgumentMatcher;
 import org.mockito.Captor;
 import org.mockito.Mock;
 import org.mockito.MockitoAnnotations;
+import org.robolectric.Robolectric;
 import org.robolectric.annotation.Config;
 
 import org.chromium.base.Promise;
@@ -95,6 +96,8 @@ public final class PageViewObserverTest {
         doReturn(false).when(mTab).isIncognito();
         doReturn(null).when(mTab).getUrlString();
         doReturn(mChromeActivity).when(mTab).getActivity();
+        doReturn(Robolectric.buildActivity(Activity.class).get()).when(mTab).getContext();
+        doReturn(Robolectric.buildActivity(Activity.class).get()).when(mTab2).getContext();
         doReturn(true).when(mTab).isInitialized();
         doReturn(true).when(mTab2).isInitialized();
         doReturn(Arrays.asList(mTabModel)).when(mTabModelSelector).getModels();

components/paint_preview/player/android/java/src/org/chromium/components/paintpreview/player/PlayerManager.java

@@ -8,6 +8,7 @@ import android.content.Context;
 import android.graphics.Rect;
 import android.view.View;
 import android.view.ViewGroup;
+import android.view.ViewGroup.LayoutParams;
 import android.widget.FrameLayout;
 
 import androidx.annotation.VisibleForTesting;
@@ -42,6 +43,8 @@ public class PlayerManager {
         mDelegate = new PlayerCompositorDelegateImpl(nativePaintPreviewServiceProvider, url,
                 directoryKey, this::onCompositorReady, linkClickHandler);
         mHostView = new FrameLayout(mContext);
+        mHostView.setLayoutParams(
+                new LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT));
         mHostView.setBackgroundColor(backgroundColor);
         mViewReadyCallback = viewReadyCallback;
     }