[M112] Fix tab is closed when back is performed on start surface

On start surface, getActivityTab still returns a valid tab. If
the tab happens to be closable or navigatable, back press is consumed
to close tab or navigate it back, rather than exiting app.

This CL adds a check to make app exit if back press is performed
on start surface.

(cherry picked from commit 85d08a1)

Bug: 1416719
Change-Id: I84d03ba11ebed34cea2bb7eeb0d01154a8785530
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4262319
Reviewed-by: Donn Denman <donnd@chromium.org>
Reviewed-by: Xi Han <hanxi@chromium.org>
Commit-Queue: Lijin Shen <lazzzis@google.com>
Code-Coverage: Findit <findit-for-me@appspot.gserviceaccount.com>
Reviewed-by: Theresa Sullivan <twellington@chromium.org>
Cr-Original-Commit-Position: refs/heads/main@{#1109268}
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4294386
Cr-Commit-Position: refs/branch-heads/5615@{#50}
Cr-Branched-From: 9c6408e-refs/heads/main@{#1109224}

chrome/android/features/start_surface/javatests/src/org/chromium/chrome/features/start_surface/StartSurfaceBackButtonTest.java

@@ -20,6 +20,7 @@
 
 import android.os.Build;
 import android.support.test.InstrumentationRegistry;
+import android.support.test.runner.lifecycle.Stage;
 import android.view.View;
 
 import androidx.test.espresso.contrib.RecyclerViewActions;
@@ -36,6 +37,7 @@
 import org.chromium.base.test.params.ParameterAnnotations.UseRunnerDelegate;
 import org.chromium.base.test.params.ParameterSet;
 import org.chromium.base.test.params.ParameterizedRunner;
+import org.chromium.base.test.util.ApplicationTestUtils;
 import org.chromium.base.test.util.CallbackHelper;
 import org.chromium.base.test.util.CommandLineFlags;
 import org.chromium.base.test.util.CriteriaHelper;
@@ -150,6 +152,39 @@ public void onFinishedShowing(@LayoutType int layoutType) {
         mMostVisitedSites = StartSurfaceTestUtils.setMVTiles(mSuggestionsDeps);
     }
 
+    // Test that back press on start surface should exit app rather than closing tab.
+    @Test
+    @MediumTest
+    @Feature({"StartSurface"})
+    @DisableFeatures({ChromeFeatureList.BACK_GESTURE_REFACTOR})
+    @CommandLineFlags.Add({START_SURFACE_TEST_SINGLE_ENABLED_PARAMS})
+    public void testShow_SingleAsHomepage_BackButton_ClosableTab() {
+        if (!mImmediateReturn) {
+            StartSurfaceTestUtils.pressHomePageButton(mActivityTestRule.getActivity());
+        }
+
+        ChromeTabbedActivity cta = mActivityTestRule.getActivity();
+        StartSurfaceTestUtils.waitForStartSurfaceVisible(
+                mLayoutChangedCallbackHelper, mCurrentlyActiveLayout, cta);
+        mActivityTestRule.loadUrlInNewTab("about:blank", false, TabLaunchType.FROM_LINK);
+        StartSurfaceTestUtils.pressHomePageButton(mActivityTestRule.getActivity());
+        StartSurfaceTestUtils.waitForStartSurfaceVisible(
+                mLayoutChangedCallbackHelper, mCurrentlyActiveLayout, cta);
+        onViewWaiting(withId(R.id.primary_tasks_surface_view));
+        StartSurfaceTestUtils.pressBack(mActivityTestRule);
+        TabUiTestHelper.verifyTabModelTabCount(cta, 2, 0);
+        ApplicationTestUtils.waitForActivityState(cta, Stage.STOPPED);
+    }
+
+    @Test
+    @MediumTest
+    @Feature({"StartSurface"})
+    @EnableFeatures({ChromeFeatureList.BACK_GESTURE_REFACTOR})
+    @CommandLineFlags.Add({START_SURFACE_TEST_SINGLE_ENABLED_PARAMS})
+    public void testShow_SingleAsHomepage_BackButton_ClosableTab_BackGestureRefactor() {
+        testShow_SingleAsHomepage_BackButton_ClosableTab();
+    }
+
     @Test
     @MediumTest
     @Feature({"StartSurface"})

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

@@ -2297,7 +2297,10 @@ && getToolbarManager().unfocusUrlBarOnBackPress()) {
             return true;
         }
 
-        final Tab currentTab = getActivityTab();
+        // crbug.com/1416719: back press on start surface should close the app.
+        final boolean isStartSurfaceHomepageShowing =
+                mStartSurfaceSupplier.hasValue() && mStartSurfaceSupplier.get().isHomepageShown();
+        final Tab currentTab = isStartSurfaceHomepageShowing ? null : getActivityTab();
         if (currentTab == null) {
             BackPressManager.record(BackPressHandler.Type.MINIMIZE_APP_AND_CLOSE_TAB);
             MinimizeAppAndCloseTabBackPressHandler.record(MinimizeAppAndCloseTabType.MINIMIZE_APP);
@@ -2379,7 +2382,9 @@ && getToolbarManager().unfocusUrlBarOnBackPress()) {
     }
 
     private void assertOnLastBackPress() {
-        var currentTab = getActivityTab();
+        final boolean isStartSurfaceHomepageShowing =
+                mStartSurfaceSupplier.hasValue() && mStartSurfaceSupplier.get().isHomepageShown();
+        final Tab currentTab = isStartSurfaceHomepageShowing ? null : getActivityTab();
         var activityTab = getActivityTabProvider().get();
         MinimizeAppAndCloseTabBackPressHandler.assertOnLastBackPress(currentTab, activityTab,
                 this::backShouldCloseTab, mLayoutStateProviderSupplier,