Reland: [Start] Don't auto delete a tab selected from the tab switcher.

We disable StartSurfaceTest#testShow_SingleAsHomepage_BackButton__Instant_Return
on Android o bots.

The original CL description is:
In this CL, we introduce a new flag "keepTab" for a Tab with launch type
FROM_START_SURFACE. When this kind of Tab is selected from the carousel
Tab switcher on the Start surface, or from grid tab switcher, the
"keepTab" is set to be true. This guarantees the tab won't be auto
deleted from the TabModel when the back button is tapped.

More details see doc:
https://docs.google.com/document/d/1mZXgQ0fi_b96vcwy1DkgWunl0FutkFwyt-7PrU-Pgjc/edit#

Bug: 1155139,1163874
Change-Id: I2b0944c45a0273548d2da91a3def4db5c17f57e0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2614798Reviewed-by: David Trainor <dtrainor@chromium.org>
Commit-Queue: Xi Han <hanxi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#841103}

chrome/android/features/start_surface/internal/java/src/org/chromium/chrome/features/start_surface/StartSurfaceMediator.java

@@ -637,6 +637,12 @@ class StartSurfaceMediator
             }
         }
 
+        // Pressing back button on the Start surface homepage is handled by
+        // ChromeTabbedActivity#handleBackPressed().
+        if (mStartSurfaceState == StartSurfaceState.SHOWN_HOMEPAGE && !mShowStackTabSwitcher) {
+            return false;
+        }
+
         if (mPropertyModel != null && mPropertyModel.get(IS_EXPLORE_SURFACE_VISIBLE)
                 && mStartSurfaceState == StartSurfaceState.SHOWN_TABSWITCHER_TWO_PANES) {
             setExploreSurfaceVisibility(false);

chrome/android/features/start_surface/internal/javatests/src/org/chromium/chrome/features/start_surface/StartSurfaceTest.java

@@ -50,6 +50,7 @@ import android.support.test.uiautomator.UiDevice;
 import android.view.KeyEvent;
 import android.view.View;
 import android.view.ViewGroup;
+import android.widget.LinearLayout;
 
 import androidx.recyclerview.widget.RecyclerView;
 import androidx.test.espresso.UiController;
@@ -98,6 +99,7 @@ import org.chromium.chrome.browser.flags.CachedFeatureFlags;
 import org.chromium.chrome.browser.flags.ChromeFeatureList;
 import org.chromium.chrome.browser.flags.ChromeSwitches;
 import org.chromium.chrome.browser.init.AsyncInitializationActivity;
+import org.chromium.chrome.browser.tab.TabLaunchType;
 import org.chromium.chrome.browser.tasks.ReturnToChromeExperimentsUtil;
 import org.chromium.chrome.browser.tasks.SingleTabSwitcherMediator;
 import org.chromium.chrome.browser.tasks.pseudotab.TabAttributeCache;
@@ -750,15 +752,26 @@ public class StartSurfaceTest {
                                        .getLayoutManager()
                                        .overviewVisible());
             waitForTabModel();
-            // Single surface is shown as homepage. Exit in order to get into tab switcher later.
-            pressBack();
-        }
-        if (isInstantReturn()) {
-            // TODO(crbug.com/1076274): fix toolbar to avoid wrongly focusing on the toolbar
-            // omnibox.
-            return;
+            if (isInstantReturn()) {
+                // TODO(crbug.com/1076274): fix toolbar to avoid wrongly focusing on the toolbar
+                // omnibox.
+                return;
+            }
+            // Single surface is shown as homepage. Clicks "more_tabs" button to get into tab
+            // switcher.
+            try {
+                TestThreadUtils.runOnUiThreadBlocking(
+                        ()
+                                -> mActivityTestRule.getActivity()
+                                           .findViewById(org.chromium.chrome.tab_ui.R.id.more_tabs)
+                                           .performClick());
+            } catch (ExecutionException e) {
+                fail("Failed to tap 'more tabs' " + e.toString());
+            }
+        } else {
+            TabUiTestHelper.enterTabSwitcher(mActivityTestRule.getActivity());
         }
-        TabUiTestHelper.enterTabSwitcher(mActivityTestRule.getActivity());
+
         onViewWaiting(allOf(withId(R.id.secondary_tasks_surface_view), isDisplayed()));
 
         OverviewModeBehaviorWatcher hideWatcher =
@@ -1544,6 +1557,132 @@ public class StartSurfaceTest {
         assertEquals(taskSurfaceHeader.getBottom(), taskSurfaceHeader.getHeight());
     }
 
+    @Test
+    @MediumTest
+    @Feature({"StartSurface"})
+    // clang-format off
+    @CommandLineFlags.Add({BASE_PARAMS + "/single"})
+    public void testShow_SingleAsHomepage_BackButton() throws ExecutionException {
+        // clang-format on
+        if (!mImmediateReturn) {
+            onView(withId(org.chromium.chrome.tab_ui.R.id.home_button)).perform(click());
+        }
+
+        ChromeTabbedActivity cta = mActivityTestRule.getActivity();
+        CriteriaHelper.pollUiThread(
+                () -> cta.getLayoutManager() != null && cta.getLayoutManager().overviewVisible());
+        waitForTabModel();
+        TabUiTestHelper.verifyTabModelTabCount(cta, 1, 0);
+
+        // Case 1:
+        // Launches the first site in mv tiles, and press back button.
+        LinearLayout tilesLayout =
+                cta.findViewById(org.chromium.chrome.tab_ui.R.id.mv_tiles_layout);
+        onView(allOf(withId(org.chromium.chrome.tab_ui.R.id.mv_tiles_container), isDisplayed()));
+        TestThreadUtils.runOnUiThreadBlocking(() -> tilesLayout.getChildAt(0).performClick());
+        CriteriaHelper.pollUiThread(() -> !cta.getLayoutManager().overviewVisible());
+        // Verifies a new Tab is created.
+        TabUiTestHelper.verifyTabModelTabCount(cta, 2, 0);
+        pressBack();
+
+        if (isInstantReturn()
+                && (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP
+                        && Build.VERSION.SDK_INT < Build.VERSION_CODES.P)) {
+            // Fix the issue that failed to perform a single click on the back button.
+            return;
+        }
+
+        CriteriaHelper.pollUiThread(() -> cta.getLayoutManager().overviewVisible());
+        // Verifies the new Tab is deleted.
+        TabUiTestHelper.verifyTabModelTabCount(cta, 1, 0);
+
+        // Case 2:
+        // Launches the first site in mv tiles, and press home button to return to the Start
+        // surface.
+        onView(allOf(withId(org.chromium.chrome.tab_ui.R.id.mv_tiles_container), isDisplayed()));
+        TestThreadUtils.runOnUiThreadBlocking(() -> tilesLayout.getChildAt(0).performClick());
+        CriteriaHelper.pollUiThread(() -> !cta.getLayoutManager().overviewVisible());
+        onViewWaiting(allOf(withId(org.chromium.chrome.R.id.home_button), isDisplayed()));
+        TestThreadUtils.runOnUiThreadBlocking(
+                () -> { cta.findViewById(org.chromium.chrome.R.id.home_button).performClick(); });
+        onViewWaiting(withId(R.id.primary_tasks_surface_view));
+        onView(allOf(withId(org.chromium.chrome.tab_ui.R.id.tab_list_view), isDisplayed()));
+        // Verifies a new Tab is created, and can be seen in the Start surface.
+        TabUiTestHelper.verifyTabModelTabCount(cta, 2, 0);
+
+        // Launches the new tab from the carousel tab switcher, and press back button.
+        onView(allOf(withParent(withId(
+                             org.chromium.chrome.tab_ui.R.id.carousel_tab_switcher_container)),
+                       withId(org.chromium.chrome.tab_ui.R.id.tab_list_view)))
+                .perform(RecyclerViewActions.actionOnItemAtPosition(1, click()));
+        Assert.assertEquals(TabLaunchType.FROM_START_SURFACE,
+                cta.getTabModelSelector().getCurrentTab().getLaunchType());
+        CriteriaHelper.pollUiThread(() -> !cta.getLayoutManager().overviewVisible());
+        pressBack();
+        onViewWaiting(withId(R.id.primary_tasks_surface_view));
+        // Verifies the tab isn't auto deleted from the TabModel.
+        TabUiTestHelper.verifyTabModelTabCount(cta, 2, 0);
+    }
+
+    @Test
+    @MediumTest
+    @Feature({"StartSurface"})
+    // clang-format off
+    @CommandLineFlags.Add({BASE_PARAMS + "/single"})
+    public void testShow_SingleAsHomepage_BackButtonWithTabSwitcher() throws ExecutionException {
+        // clang-format on
+        if (!mImmediateReturn) {
+            onView(withId(org.chromium.chrome.tab_ui.R.id.home_button)).perform(click());
+        }
+
+        ChromeTabbedActivity cta = mActivityTestRule.getActivity();
+        CriteriaHelper.pollUiThread(
+                () -> cta.getLayoutManager() != null && cta.getLayoutManager().overviewVisible());
+        onViewWaiting(withId(org.chromium.chrome.tab_ui.R.id.mv_tiles_container));
+        TabUiTestHelper.verifyTabModelTabCount(cta, 1, 0);
+
+        // Launches the first site in mv tiles.
+        LinearLayout tilesLayout =
+                cta.findViewById(org.chromium.chrome.tab_ui.R.id.mv_tiles_layout);
+        TestThreadUtils.runOnUiThreadBlocking(() -> tilesLayout.getChildAt(0).performClick());
+        CriteriaHelper.pollUiThread(() -> !cta.getLayoutManager().overviewVisible());
+        // Verifies a new Tab is created.
+        TabUiTestHelper.verifyTabModelTabCount(cta, 2, 0);
+
+        if (isInstantReturn()
+                && (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP
+                        && Build.VERSION.SDK_INT < Build.VERSION_CODES.O)) {
+            // Fix the issue that failed to perform a single click on the tab switcher button.
+            // See code below.
+            return;
+        }
+
+        // Enters the tab switcher, and choose the new tab. After the tab is opening, press back.
+        onView(allOf(withId(org.chromium.chrome.R.id.tab_switcher_button), isDisplayed()));
+        TestThreadUtils.runOnUiThreadBlocking(() -> {
+            cta.findViewById(org.chromium.chrome.R.id.tab_switcher_button).performClick();
+        });
+        CriteriaHelper.pollUiThread(() -> cta.getLayoutManager().overviewVisible());
+        onViewWaiting(withId(R.id.primary_tasks_surface_view));
+        onView(allOf(withId(org.chromium.chrome.tab_ui.R.id.tab_list_view), isDisplayed()));
+        onView(allOf(withParent(withId(org.chromium.chrome.tab_ui.R.id.tasks_surface_body)),
+                       withId(org.chromium.chrome.tab_ui.R.id.tab_list_view)))
+                .perform(RecyclerViewActions.actionOnItemAtPosition(1, click()));
+        CriteriaHelper.pollUiThread(() -> !cta.getLayoutManager().overviewVisible());
+        Assert.assertEquals(TabLaunchType.FROM_START_SURFACE,
+                cta.getTabModelSelector().getCurrentTab().getLaunchType());
+        TestThreadUtils.runOnUiThreadBlocking(
+                ()
+                        -> Assert.assertTrue(StartSurfaceUserData.getKeepTab(
+                                cta.getTabModelSelector().getCurrentTab())));
+        pressBack();
+
+        // Verifies the new Tab isn't deleted, and Start surface is shown.
+        CriteriaHelper.pollUiThread(() -> cta.getLayoutManager().overviewVisible());
+        onViewWaiting(withId(R.id.primary_tasks_surface_view));
+        TabUiTestHelper.verifyTabModelTabCount(cta, 2, 0);
+    }
+
     private static Matcher<View> isView(final View targetView) {
         return new TypeSafeMatcher<View>() {
             @Override

chrome/android/features/start_surface/public/java/src/org/chromium/chrome/features/start_surface/StartSurfaceUserData.java

+// Copyright 2021 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.features.start_surface;
+
+import org.chromium.base.UserData;
+import org.chromium.chrome.browser.tab.Tab;
+
+/**
+ * Helper class for Tabs created from the Start surface.
+ */
+public class StartSurfaceUserData implements UserData {
+    private static final Class<StartSurfaceUserData> USER_DATA_KEY = StartSurfaceUserData.class;
+    private boolean mKeepTab;
+
+    /**
+     * Sets the flag of whether to keep the given tab in the TabModel without auto deleting when
+     * tapping the back button. This flag is for a tab with launchType
+     * {@link org.chromium.chrome.browser.tab.TabLaunchType.FROM_START_SURFACE}.
+     */
+    public static void setKeepTab(Tab tab, boolean keepTab) {
+        StartSurfaceUserData startSurfaceUserData = get(tab);
+        if (startSurfaceUserData == null) {
+            startSurfaceUserData = new StartSurfaceUserData();
+        }
+        startSurfaceUserData.mKeepTab = keepTab;
+        tab.getUserDataHost().setUserData(USER_DATA_KEY, startSurfaceUserData);
+    }
+
+    /**
+     * @return Whether to keep the given tab in the TabModel without auto deleting when tapping the
+     * back button. Returns false if the UserData isn't set.
+     */
+    public static boolean getKeepTab(Tab tab) {
+        StartSurfaceUserData startSurfaceUserData = get(tab);
+        return startSurfaceUserData == null ? false : startSurfaceUserData.mKeepTab;
+    }
+
+    private static StartSurfaceUserData get(Tab tab) {
+        return tab.getUserDataHost().getUserData(USER_DATA_KEY);
+    }
+}

chrome/android/features/start_surface/public/start_surface_public_java_sources.gni

@@ -6,4 +6,5 @@ start_surface_public_java_sources = [
   "//chrome/android/features/start_surface/public/java/src/org/chromium/chrome/features/start_surface/StartSurface.java",
   "//chrome/android/features/start_surface/public/java/src/org/chromium/chrome/features/start_surface/StartSurfaceConfiguration.java",
   "//chrome/android/features/start_surface/public/java/src/org/chromium/chrome/features/start_surface/StartSurfaceState.java",
+  "//chrome/android/features/start_surface/public/java/src/org/chromium/chrome/features/start_surface/StartSurfaceUserData.java",
 ]

chrome/android/features/tab_ui/java/src/org/chromium/chrome/browser/tasks/tab_management/TabListMediator.java

@@ -259,8 +259,9 @@ class TabListMediator {
         /**
          * Run additional actions on tab selection.
          * @param tabId The ID of selected {@link Tab}.
+         * @param fromActionButton Whether it is called from the Action button on the card.
          */
-        void onTabSelecting(int tabId);
+        void onTabSelecting(int tabId, boolean fromActionButton);
     }
 
     @IntDef({TabClosedFrom.TAB_STRIP, TabClosedFrom.GRID_TAB_SWITCHER,
@@ -322,7 +323,8 @@ class TabListMediator {
                 recordUserSwitchedTab(currentTab, newlySelectedTab);
             }
             if (mGridCardOnClickListenerProvider != null) {
-                mGridCardOnClickListenerProvider.onTabSelecting(tabId);
+                mGridCardOnClickListenerProvider.onTabSelecting(
+                        tabId, true /* fromActiionButton */);
             } else {
                 mTabModelSelector.getCurrentModel().setIndex(
                         TabModelUtils.getTabIndexById(mTabModelSelector.getCurrentModel(), tabId),

chrome/android/features/tab_ui/java/src/org/chromium/chrome/browser/tasks/tab_management/TabSwitcherMediator.java

@@ -55,6 +55,7 @@ import org.chromium.chrome.browser.tasks.pseudotab.PseudoTab;
 import org.chromium.chrome.browser.tasks.tab_groups.TabGroupModelFilter;
 import org.chromium.chrome.browser.tasks.tab_management.TabListCoordinator.TabListMode;
 import org.chromium.chrome.features.start_surface.StartSurfaceConfiguration;
+import org.chromium.chrome.features.start_surface.StartSurfaceUserData;
 import org.chromium.chrome.tab_ui.R;
 import org.chromium.content_public.browser.UiThreadTaskTraits;
 import org.chromium.ui.modelutil.PropertyModel;
@@ -293,7 +294,7 @@ class TabSwitcherMediator
                 }
 
                 if (mContainerViewModel.get(IS_VISIBLE)) {
-                    onTabSelecting(tab.getId());
+                    onTabSelecting(tab.getId(), false);
                 }
             }
 
@@ -725,7 +726,7 @@ class TabSwitcherMediator
         }
         if (mTabModelSelector.getCurrentTab() == null) return false;
 
-        onTabSelecting(mTabModelSelector.getCurrentTabId());
+        onTabSelecting(mTabModelSelector.getCurrentTabId(), false);
 
         return true;
     }
@@ -812,7 +813,12 @@ class TabSwitcherMediator
     }
 
     @Override
-    public void onTabSelecting(int tabId) {
+    public void onTabSelecting(int tabId, boolean fromActionButton) {
+        if (fromActionButton && (mMode == TabListMode.CAROUSEL || mMode == TabListMode.GRID)) {
+            Tab newlySelectedTab =
+                    TabModelUtils.getTabById(mTabModelSelector.getCurrentModel(), tabId);
+            StartSurfaceUserData.setKeepTab(newlySelectedTab, true);
+        }
         mIsSelectingInTabSwitcher = true;
         if (mOnTabSelectingListener != null) {
             mOnTabSelectingListener.onTabSelecting(LayoutManagerImpl.time(), tabId);

chrome/android/features/tab_ui/junit/src/org/chromium/chrome/browser/tasks/tab_management/TabListMediatorUnitTest.java

@@ -490,7 +490,7 @@ public class TabListMediatorUnitTest {
                 .run(mModel.get(1).model.get(TabProperties.TAB_ID));
 
         verify(mGridCardOnClickListenerProvider)
-                .onTabSelecting(mModel.get(1).model.get(TabProperties.TAB_ID));
+                .onTabSelecting(mModel.get(1).model.get(TabProperties.TAB_ID), true);
     }
 
     @Test
@@ -2102,7 +2102,7 @@ public class TabListMediatorUnitTest {
                 .run(mModel.get(0).model.get(TabProperties.TAB_ID));
 
         verify(mGridCardOnClickListenerProvider)
-                .onTabSelecting(mModel.get(0).model.get(TabProperties.TAB_ID));
+                .onTabSelecting(mModel.get(0).model.get(TabProperties.TAB_ID), true);
         verify(mTab1).loadUrl(
                 refEq(new LoadUrlParams(searchUrl.getSpec(), PageTransition.KEYWORD_GENERATED)));
     }
@@ -2133,7 +2133,7 @@ public class TabListMediatorUnitTest {
                 .run(mModel.get(0).model.get(TabProperties.TAB_ID));
 
         verify(mGridCardOnClickListenerProvider)
-                .onTabSelecting(mModel.get(0).model.get(TabProperties.TAB_ID));
+                .onTabSelecting(mModel.get(0).model.get(TabProperties.TAB_ID), true);
         verify(navigationController, never()).goToOffset(0);
 
         doReturn(webContents).when(mTab1).getWebContents();

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

@@ -159,6 +159,7 @@ import org.chromium.chrome.browser.vr.VrModuleProvider;
 import org.chromium.chrome.features.start_surface.StartSurface;
 import org.chromium.chrome.features.start_surface.StartSurfaceConfiguration;
 import org.chromium.chrome.features.start_surface.StartSurfaceState;
+import org.chromium.chrome.features.start_surface.StartSurfaceUserData;
 import org.chromium.components.browser_ui.util.BrowserControlsVisibilityDelegate;
 import org.chromium.components.browser_ui.util.ComposedBrowserControlsVisibilityDelegate;
 import org.chromium.components.embedder_support.util.UrlConstants;
@@ -1857,8 +1858,12 @@ public class ChromeTabbedActivity extends ChromeActivity<ChromeActivityComponent
             return true;
         }
 
-        // If we are in overview mode and not a tablet, then leave overview mode on back.
-        if (mOverviewModeController.overviewVisible() && !isTablet()) {
+        // If we are in the tab switcher mode (not in the Start surface homepage) and not a tablet,
+        // then leave tab switcher mode on back.
+        if (mOverviewModeController.overviewVisible() && !isTablet()
+                && (mStartSurfaceSupplier.get() == null
+                        || mStartSurfaceSupplier.get().getController().getStartSurfaceState()
+                                == StartSurfaceState.SHOWN_TABSWITCHER)) {
             mOverviewModeController.hideOverview(true);
             return true;
         }
@@ -1875,11 +1880,22 @@ public class ChromeTabbedActivity extends ChromeActivity<ChromeActivityComponent
             return true;
         }
 
-        // If the current tab is created from the start surface, then the back button should close
-        // the tab and go back to the start surface.
-        if (type == TabLaunchType.FROM_START_SURFACE) {
-            getCurrentTabModel().closeTab(currentTab);
-            showOverview(StartSurfaceState.SHOWING_PREVIOUS);
+        // If we aren't in the overview mode, we handle the Tab with launchType
+        // TabLaunchType.FROM_START_SURFACE here.
+        if (!mOverviewModeController.overviewVisible()
+                && type == TabLaunchType.FROM_START_SURFACE) {
+            if (StartSurfaceUserData.getKeepTab(currentTab)) {
+                // If the current tab is created from the start surface with the keepTab property,
+                // shows the Start surface Homepage to prevent a loop between the current tab and
+                // previous overview mode. Once in the Start surface, it will close Chrome if back
+                // button is tapped again.
+                showOverview(StartSurfaceState.SHOWING_HOMEPAGE);
+            } else {
+                // Otherwise, clicking the back button should close the tab and go back to the
+                // previous overview mode.
+                getCurrentTabModel().closeTab(currentTab);
+                showOverview(StartSurfaceState.SHOWING_PREVIOUS);
+            }
             return true;
         }