[duet] start test activity on blank page instead of ntp

The tests are flaky on Android K & L. It shows the ntp is scrolled down
on launching the activity, but the reason has not been figured out.
Launching activity on blank page can prevent the startpage from being
scrolled down.

Bug: 1046317, 1046316, 1045729, 1045415
Change-Id: I1d14f15218ad8a1e1ceac9c0a7bbfc1d49008700
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2028212Reviewed-by: Theresa  <twellington@chromium.org>
Reviewed-by: Wei-Yin Chen (陳威尹) <wychen@chromium.org>
Reviewed-by: Yue Zhang <yuezhanggg@chromium.org>
Commit-Queue: Lijin Shen <lazzzis@google.com>
Cr-Commit-Position: refs/heads/master@{#738263}

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

@@ -507,6 +507,7 @@ public class TabUiTestHelper {
             CriteriaHelper.pollUiThread(
                     Criteria.equals(mExpectedCount, () -> adapter.getItemCount()));
 
+            recyclerView.setItemAnimator(null); // Disable animation to reduce flakiness.
             for (int i = 0; i < mExpectedCount; i++) {
                 RecyclerView.ViewHolder viewHolder =
                         recyclerView.findViewHolderForAdapterPosition(i);

chrome/android/javatests/src/org/chromium/chrome/browser/toolbar/top/AdaptiveToolbarTest.java

@@ -24,7 +24,6 @@ import static org.chromium.chrome.test.util.ToolbarTestUtils.checkToolbarVisibil
 
 import android.content.pm.ActivityInfo;
 import android.content.res.Configuration;
-import android.os.Build;
 import android.support.test.filters.MediumTest;
 
 import org.junit.After;
@@ -35,8 +34,6 @@ import org.junit.rules.TestRule;
 import org.junit.runner.RunWith;
 
 import org.chromium.base.test.util.CommandLineFlags;
-import org.chromium.base.test.util.DisableIf;
-import org.chromium.base.test.util.DisabledTest;
 import org.chromium.base.test.util.Restriction;
 import org.chromium.chrome.browser.ChromeSwitches;
 import org.chromium.chrome.browser.ChromeTabbedActivity;
@@ -86,7 +83,7 @@ public class AdaptiveToolbarTest {
             boolean isBottomToolbarEnabled, boolean isGridTabSwitcherEnabled) {
         FeatureUtilities.setGridTabSwitcherEnabledForTesting(isGridTabSwitcherEnabled);
         FeatureUtilities.setIsBottomToolbarEnabledForTesting(isBottomToolbarEnabled);
-        mActivityTestRule.startMainActivityFromLauncher();
+        mActivityTestRule.startMainActivityOnBlankPage();
         CriteriaHelper.pollUiThread(mActivityTestRule.getActivity()
                                             .getTabModelSelector()
                                             .getTabModelFilterProvider()
@@ -130,11 +127,8 @@ public class AdaptiveToolbarTest {
     @Test
     @MediumTest
     // clang-format off
-    @DisableIf.Build(message = "Flaky on KitKat: crbug.com/1046317",
-            sdk_is_less_than = Build.VERSION_CODES.LOLLIPOP)
     @CommandLineFlags.Add({"enable-features=" + ChromeFeatureList.TAB_GRID_LAYOUT_ANDROID +
             "<Study", "force-fieldtrials=Study/Group", NO_NEW_TAB_VARIATION_PARAMS})
-    @DisabledTest(message = "crbug.com/1046748")
     public void testTopToolbar_WithGTS_WithBottomToolbar_Home_Search_Tab_Switcher_IncognitoDisabled() {
         // clang-format on
         IncognitoUtils.setEnabledForTesting(false);
@@ -172,8 +166,6 @@ public class AdaptiveToolbarTest {
     @Test
     @MediumTest
     // clang-format off
-    @DisableIf.Build(message = "Flaky on KitKat: crbug.com/1046316",
-            sdk_is_less_than = Build.VERSION_CODES.LOLLIPOP)
     @CommandLineFlags.Add({"enable-features=" + ChromeFeatureList.TAB_GRID_LAYOUT_ANDROID +
             "<Study", "force-fieldtrials=Study/Group", NO_NEW_TAB_VARIATION_PARAMS})
     public void testTopToolbar_WithGTS_WithBottomToolbar_Home_Search_Share() {
@@ -263,7 +255,6 @@ public class AdaptiveToolbarTest {
 
     @Test
     @MediumTest
-    @DisableIf.Build(message = "Flaky test: https://crbug.com/1045415")
     public void testTopToolbar_WithoutGTS_WithBottomToolbar_Home_Search_Tab_Switcher() {
         BottomToolbarVariationManager.setVariation(Variations.HOME_SEARCH_TAB_SWITCHER);
         setupFlagsAndLaunchActivity(true, false);
@@ -294,11 +285,7 @@ public class AdaptiveToolbarTest {
 
     @Test
     @MediumTest
-    // clang-format off
-    @DisableIf.Build(message = "Flaky on KitKat: crbug.com/1045729",
-            sdk_is_less_than = Build.VERSION_CODES.LOLLIPOP)
     public void testTopToolbar_WithoutGTS_WithBottomToolbar_Home_Search_Share() {
-        // clang-format on
         BottomToolbarVariationManager.setVariation(Variations.HOME_SEARCH_SHARE);
         setupFlagsAndLaunchActivity(true, false);
         final ChromeTabbedActivity cta = mActivityTestRule.getActivity();