Enable drag-and-drop for StartSurface variations without MRU ordering

Bug: 1005931
Change-Id: Ie56ba62a695b9895fdd5b67ef9547aa8c59bc1fc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1893507
Commit-Queue: Yue Zhang <yuezhanggg@chromium.org>
Reviewed-by: Wei-Yin Chen (陳威尹) <wychen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#711758}

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

@@ -83,13 +83,14 @@ public class TabGridItemTouchHelperCallback extends ItemTouchHelper.SimpleCallba
         boolean isTabGroupEnabled = FeatureUtilities.isTabGroupsAndroidEnabled();
         boolean isTabGroupUiImprovementEnabled =
                 FeatureUtilities.isTabGroupsAndroidUiImprovementsEnabled();
-        boolean isStartSurfaceEnabled = FeatureUtilities.isStartSurfaceEnabled();
+        boolean isMRUEnabledInTabSwitcher =
+                TabSwitcherMediator.isShowingTabsInMRUOrder() && mActionsOnAllRelatedTabs;
         // Only enable drag for users with group disabled, or with group and group ui improvement
-        // enabled at the same time. Also, disable drag for start surface for now.
+        // enabled at the same time. Also, disable drag for MRU-order tab switcher in start surface.
         // TODO(crbug.com/1005931): Figure out how drag-to-reorder lives in StartSurface MRU
         // ordering scenario.
-        boolean isDragEnabled =
-                !isStartSurfaceEnabled && (!isTabGroupEnabled || isTabGroupUiImprovementEnabled);
+        boolean isDragEnabled = !isMRUEnabledInTabSwitcher
+                && (!isTabGroupEnabled || isTabGroupUiImprovementEnabled);
         mDragFlags = isDragEnabled ? ItemTouchHelper.START | ItemTouchHelper.END
                         | ItemTouchHelper.UP | ItemTouchHelper.DOWN
                                    : 0;

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

@@ -133,7 +133,7 @@ public class TabSwitcherCoordinator implements Destroyable, TabSwitcher,
 
         if (FeatureUtilities.isTabGroupsAndroidUiImprovementsEnabled()
                 && mode == TabListCoordinator.TabListMode.GRID
-                && !FeatureUtilities.isStartSurfaceEnabled()) {
+                && !TabSwitcherMediator.isShowingTabsInMRUOrder()) {
             mTabGridIphItemCoordinator = new TabGridIphItemCoordinator(
                     context, mTabListCoordinator.getContainerView(), container);
             mMediator.setIphProvider(mTabGridIphItemCoordinator.getIphProvider());

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

@@ -275,9 +275,7 @@ class TabSwitcherMediator implements TabSwitcher.Controller, TabListRecyclerView
 
         // TODO(crbug.com/982018): Let the start surface pass in the parameter and add unit test for
         // it. This is a temporary solution to keep this change minimum.
-        String feature = ChromeFeatureList.getFieldTrialParamByFeature(
-                ChromeFeatureList.START_SURFACE_ANDROID, "start_surface_variation");
-        mShowTabsInMruOrder = feature.equals("twopanes") || feature.equals("single");
+        mShowTabsInMruOrder = isShowingTabsInMRUOrder();
     }
 
     /**
@@ -538,6 +536,16 @@ class TabSwitcherMediator implements TabSwitcher.Controller, TabListRecyclerView
         mIphProvider = iphProvider;
     }
 
+    /**
+     * Check if tabs should show in MRU order in current start surface tab switcher.
+     *  @return whether tabs should show in MRU order
+     */
+    static boolean isShowingTabsInMRUOrder() {
+        String feature = ChromeFeatureList.getFieldTrialParamByFeature(
+                ChromeFeatureList.START_SURFACE_ANDROID, "start_surface_variation");
+        return feature.equals("twopanes") || feature.equals("single");
+    }
+
     /**
      * Destroy any members that needs clean up.
      */