Enable drop-to-merge in GTS

This CL enables dropping a tab on another tab to form a group. It is
behind the TabGroupsAndroidUiImprovements flag.

Bug: 963692
Change-Id: I1cb49a20459972af3c02bdc7c9ebb9480209de29
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1615606Reviewed-by: Ilya Sherman <isherman@chromium.org>
Reviewed-by: Yusuf Ozuysal <yusufo@chromium.org>
Commit-Queue: Yue Zhang <yuezhanggg@google.com>
Cr-Commit-Position: refs/heads/master@{#666450}

chrome/android/features/tab_ui/BUILD.gn

@@ -29,6 +29,7 @@ android_library("java") {
     "java/src/org/chromium/chrome/browser/tasks/tab_management/TabGridDialogCoordinator.java",
     "java/src/org/chromium/chrome/browser/tasks/tab_management/TabGridDialogMediator.java",
     "java/src/org/chromium/chrome/browser/tasks/tab_management/TabGridDialogParent.java",
+    "java/src/org/chromium/chrome/browser/tasks/tab_management/TabGridItemTouchHelperCallback.java",
     "java/src/org/chromium/chrome/browser/tasks/tab_management/TabGridSheetCoordinator.java",
     "java/src/org/chromium/chrome/browser/tasks/tab_management/TabGridSheetMediator.java",
     "java/src/org/chromium/chrome/browser/tasks/tab_management/TabGridSheetContent.java",

chrome/android/features/tab_ui/java/res/values/dimens.xml

@@ -12,6 +12,7 @@
     <dimen name="tab_grid_close_button_size">18dp</dimen>
     <dimen name="tab_grid_dialog_side_margin">16dp</dimen>
     <dimen name="tab_grid_dialog_top_margin">85dp</dimen>
+    <dimen name="tab_grid_merge_threshold">45dp</dimen>
     <dimen name="tab_grid_thumbnail_card_default_size">152dp</dimen>
     <dimen name="tab_grid_thumbnail_favicon_frame_padding">16dp</dimen>
     <dimen name="tab_grid_thumbnail_favicon_padding">24dp</dimen>

chrome/android/features/tab_ui/java/src/org/chromium/chrome/browser/tasks/tab_groups/TabGroupUtils.java

@@ -12,6 +12,7 @@ import org.chromium.chrome.browser.ChromeFeatureList;
 import org.chromium.chrome.browser.feature_engagement.TrackerFactory;
 import org.chromium.chrome.browser.profiles.Profile;
 import org.chromium.chrome.browser.tab.Tab;
+import org.chromium.chrome.browser.tabmodel.TabModel;
 import org.chromium.chrome.browser.tabmodel.TabModelSelector;
 import org.chromium.chrome.browser.tabmodel.TabModelSelectorTabObserver;
 import org.chromium.chrome.browser.tasks.tabgroup.TabGroupModelFilter;
@@ -110,25 +111,25 @@ public class TabGroupUtils {
 
     /**
      * This method gets the index in TabModel of the first tab in {@code tabs}.
-     * @param selector   The selector that owns the {@code tab}.
+     * @param tabModel   The tabModel that owns the {@code tab}.
      * @param tabs       The list of tabs among which we need to find the first tab index.
      * @return The index in TabModel of the first tab in {@code tabs}
      */
-    public static int getFirstTabModelIndexForList(TabModelSelector selector, List<Tab> tabs) {
+    public static int getFirstTabModelIndexForList(TabModel tabModel, List<Tab> tabs) {
         assert tabs != null && tabs.size() != 0;
 
-        return selector.getCurrentModel().indexOf(tabs.get(0));
+        return tabModel.indexOf(tabs.get(0));
     }
 
     /**
      * This method gets the index in TabModel of the last tab in {@code tabs}.
-     * @param selector   The selector that owns the {@code tab}.
+     * @param tabModel   The tabModel that owns the {@code tab}.
      * @param tabs       The list of tabs among which we need to find the last tab index.
      * @return The index in TabModel of the last tab in {@code tabs}
      */
-    public static int getLastTabModelIndexForList(TabModelSelector selector, List<Tab> tabs) {
+    public static int getLastTabModelIndexForList(TabModel tabModel, List<Tab> tabs) {
         assert tabs != null && tabs.size() != 0;
 
-        return selector.getCurrentModel().indexOf(tabs.get(tabs.size() - 1));
+        return tabModel.indexOf(tabs.get(tabs.size() - 1));
     }
 }

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

+// Copyright 2019 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.tasks.tab_management;
+
+import android.graphics.Canvas;
+import android.support.v7.widget.RecyclerView;
+import android.support.v7.widget.helper.ItemTouchHelper;
+
+import org.chromium.base.VisibleForTesting;
+import org.chromium.base.metrics.RecordUserAction;
+import org.chromium.chrome.browser.tab.Tab;
+import org.chromium.chrome.browser.tabmodel.EmptyTabModelFilter;
+import org.chromium.chrome.browser.tabmodel.TabModel;
+import org.chromium.chrome.browser.tabmodel.TabModelFilter;
+import org.chromium.chrome.browser.tabmodel.TabModelSelector;
+import org.chromium.chrome.browser.tasks.tab_groups.TabGroupUtils;
+import org.chromium.chrome.browser.tasks.tabgroup.TabGroupModelFilter;
+
+import java.util.List;
+
+/**
+ * A {@link ItemTouchHelper.SimpleCallback} implementation to host the logic for swipe and drag
+ * related actions in grid related layouts.
+ * TODO(yuezhanggg): Get rid of using notifyDataSetChanged in adapter.
+ */
+public class TabGridItemTouchHelperCallback extends ItemTouchHelper.SimpleCallback {
+    /**
+     * An interface to update information in {@link TabListModel}.
+     */
+    public interface UpdateTabInfoHandler {
+        void updateTabInfo(int index, Tab tab, boolean isSelected);
+    }
+
+    private final TabListModel mModel;
+    private final TabModelSelector mTabModelSelector;
+    private final TabListMediator.TabActionListener mTabClosedListener;
+    private final String mComponentName;
+    private final UpdateTabInfoHandler mUpdateTabHandler;
+    private float mSwipeToDismissThreshold;
+    private float mMergeThreshold;
+    private boolean mActionsOnAllRelatedTabs;
+    private int mDragFlags;
+    private int mSelectedTabIndex = TabModel.INVALID_TAB_INDEX;
+    private int mHoveredTabIndex = TabModel.INVALID_TAB_INDEX;
+    private RecyclerView mRecyclerView;
+
+    public TabGridItemTouchHelperCallback(TabListModel tabListModel,
+            TabModelSelector tabModelSelector, TabListMediator.TabActionListener tabClosedListener,
+            UpdateTabInfoHandler updateTabHandler, String componentName,
+            boolean actionsOnAllRelatedTabs) {
+        super(0, 0);
+        mModel = tabListModel;
+        mTabModelSelector = tabModelSelector;
+        mTabClosedListener = tabClosedListener;
+        mUpdateTabHandler = updateTabHandler;
+        mComponentName = componentName;
+        mActionsOnAllRelatedTabs = actionsOnAllRelatedTabs;
+    }
+
+    /**
+     * This method sets up parameters that are used by the {@link ItemTouchHelper} to make decisions
+     * about user actions.
+     * @param swipeToDismissThreshold   Defines the threshold that user needs to swipe in order to
+     *         be considered as a remove operation.
+     * @param mergeThreshold            Defines the threshold of how much two items need to be
+     *         overlapped in order to be considered as a merge operation.
+     * @param isDragEnabled             Whether drag related behavior should handled in this
+     *         callback.
+     */
+    void setupCallback(float swipeToDismissThreshold, float mergeThreshold, boolean isDragEnabled) {
+        mSwipeToDismissThreshold = swipeToDismissThreshold;
+        mMergeThreshold = mergeThreshold;
+        mDragFlags = isDragEnabled ? ItemTouchHelper.START | ItemTouchHelper.END
+                        | ItemTouchHelper.UP | ItemTouchHelper.DOWN
+                                   : 0;
+    }
+
+    @Override
+    public int getMovementFlags(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder) {
+        final int dragFlags = mDragFlags;
+        final int swipeFlags = ItemTouchHelper.START | ItemTouchHelper.END;
+        mRecyclerView = recyclerView;
+        return makeMovementFlags(dragFlags, swipeFlags);
+    }
+
+    @Override
+    public boolean onMove(RecyclerView recyclerView, RecyclerView.ViewHolder fromViewHolder,
+            RecyclerView.ViewHolder toViewHolder) {
+        assert fromViewHolder instanceof TabGridViewHolder;
+        assert toViewHolder instanceof TabGridViewHolder;
+
+        RecordUserAction.record("TabGrid.DragToReorder." + mComponentName);
+        mSelectedTabIndex = toViewHolder.getAdapterPosition();
+        if (mHoveredTabIndex != -1) {
+            mModel.updateHoveredTabForMergeToGroup(mHoveredTabIndex, false);
+            mHoveredTabIndex = -1;
+        }
+
+        int currentTabId = ((TabGridViewHolder) fromViewHolder).getTabId();
+        int destinationTabId = ((TabGridViewHolder) toViewHolder).getTabId();
+        int distance = toViewHolder.getAdapterPosition() - fromViewHolder.getAdapterPosition();
+        TabModelFilter filter =
+                mTabModelSelector.getTabModelFilterProvider().getCurrentTabModelFilter();
+        TabModel tabModel = mTabModelSelector.getCurrentModel();
+        if (filter instanceof EmptyTabModelFilter) {
+            tabModel.moveTab(currentTabId,
+                    mModel.indexFromId(currentTabId) + (distance > 0 ? distance + 1 : distance));
+        } else if (!mActionsOnAllRelatedTabs) {
+            int destinationIndex = tabModel.indexOf(mTabModelSelector.getTabById(destinationTabId));
+            tabModel.moveTab(currentTabId, distance > 0 ? destinationIndex + 1 : destinationIndex);
+        } else {
+            List<Tab> destinationTabGroup = getRelatedTabsForId(destinationTabId);
+            int newIndex = distance >= 0
+                    ? TabGroupUtils.getLastTabModelIndexForList(tabModel, destinationTabGroup) + 1
+                    : TabGroupUtils.getFirstTabModelIndexForList(tabModel, destinationTabGroup);
+            ((TabGroupModelFilter) filter).moveRelatedTabs(currentTabId, newIndex);
+        }
+        return true;
+    }
+
+    @Override
+    public void onSwiped(RecyclerView.ViewHolder viewHolder, int i) {
+        assert viewHolder instanceof TabGridViewHolder;
+
+        mTabClosedListener.run(((TabGridViewHolder) viewHolder).getTabId());
+        RecordUserAction.record("MobileStackViewSwipeCloseTab." + mComponentName);
+    }
+
+    @Override
+    public void onSelectedChanged(RecyclerView.ViewHolder viewHolder, int actionState) {
+        if (actionState == ItemTouchHelper.ACTION_STATE_DRAG) {
+            mSelectedTabIndex = viewHolder.getAdapterPosition();
+            mModel.updateSelectedTabForMergeToGroup(mSelectedTabIndex, true);
+        } else if (actionState == ItemTouchHelper.ACTION_STATE_IDLE) {
+            if (mHoveredTabIndex != -1 && mActionsOnAllRelatedTabs) {
+                RecordUserAction.record("GridTabSwitcher.DropTabToMerge");
+                onTabMergeToGroup(mSelectedTabIndex, mHoveredTabIndex);
+                mRecyclerView.getAdapter().notifyDataSetChanged();
+            }
+            if (mHoveredTabIndex == -1) {
+                mModel.updateSelectedTabForMergeToGroup(mSelectedTabIndex, false);
+            }
+            mHoveredTabIndex = -1;
+            mSelectedTabIndex = -1;
+        }
+    }
+
+    @Override
+    public void onChildDraw(Canvas c, RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder,
+            float dX, float dY, int actionState, boolean isCurrentlyActive) {
+        super.onChildDraw(c, recyclerView, viewHolder, dX, dY, actionState, isCurrentlyActive);
+        if (actionState == ItemTouchHelper.ACTION_STATE_SWIPE) {
+            float alpha = Math.max(0.2f, 1f - 0.8f * Math.abs(dX) / mSwipeToDismissThreshold);
+            int index = mModel.indexFromId(((TabGridViewHolder) viewHolder).getTabId());
+            if (index == -1) return;
+
+            mModel.get(index).set(TabProperties.ALPHA, alpha);
+        } else if (actionState == ItemTouchHelper.ACTION_STATE_DRAG && mActionsOnAllRelatedTabs) {
+            int prev_hovered = mHoveredTabIndex;
+            mHoveredTabIndex = TabListRecyclerView.getHoveredTabIndex(
+                    recyclerView, viewHolder.itemView, dX, dY, mMergeThreshold);
+            mModel.updateHoveredTabForMergeToGroup(mHoveredTabIndex, true);
+            if (prev_hovered != mHoveredTabIndex) {
+                mModel.updateHoveredTabForMergeToGroup(prev_hovered, false);
+            }
+        }
+    }
+
+    @Override
+    public float getSwipeThreshold(RecyclerView.ViewHolder viewHolder) {
+        return mSwipeToDismissThreshold / viewHolder.itemView.getWidth();
+    }
+
+    private List<Tab> getRelatedTabsForId(int id) {
+        return mTabModelSelector.getTabModelFilterProvider()
+                .getCurrentTabModelFilter()
+                .getRelatedTabList(id);
+    }
+
+    private void onTabMergeToGroup(int selectedCardIndex, int hoveredCardIndex) {
+        mModel.updateHoveredTabForMergeToGroup(hoveredCardIndex, false);
+        TabGroupModelFilter filter =
+                (TabGroupModelFilter) mTabModelSelector.getTabModelFilterProvider()
+                        .getCurrentTabModelFilter();
+        filter.mergeTabsToGroup(filter.getTabAt(selectedCardIndex).getId(),
+                filter.getTabAt(hoveredCardIndex).getId());
+        int destinationIndex =
+                selectedCardIndex > hoveredCardIndex ? hoveredCardIndex : hoveredCardIndex - 1;
+        Tab newSelectedTab = filter.getTabAt(destinationIndex);
+        boolean isSelected = newSelectedTab.getId() == mTabModelSelector.getCurrentTabId();
+        mUpdateTabHandler.updateTabInfo(destinationIndex, newSelectedTab, isSelected);
+    }
+
+    @VisibleForTesting
+    void setActionsOnAllRelatedTabsForTest(boolean flag) {
+        mActionsOnAllRelatedTabs = flag;
+    }
+
+    @VisibleForTesting
+    void setHoveredTabIndexForTest(int index) {
+        mHoveredTabIndex = index;
+    }
+
+    @VisibleForTesting
+    void setSelectedTabIndexForTest(int index) {
+        mSelectedTabIndex = index;
+    }
+}

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

@@ -111,6 +111,9 @@ class TabGridViewBinder {
         } else if (TabProperties.IPH_PROVIDER == propertyKey) {
             TabListMediator.IphProvider provider = item.get(TabProperties.IPH_PROVIDER);
             if (provider != null) provider.showIPH(holder.thumbnail);
+        } else if (TabProperties.CARD_ANIMATION_STATUS == propertyKey) {
+            TabListRecyclerView.scaleTabGridCardView(
+                    holder.itemView, item.get(TabProperties.CARD_ANIMATION_STATUS));
         }
     }
 

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

@@ -22,6 +22,7 @@ import org.chromium.chrome.browser.profiles.Profile;
 import org.chromium.chrome.browser.tab.Tab;
 import org.chromium.chrome.browser.tabmodel.TabModelSelector;
 import org.chromium.chrome.browser.tasks.tab_groups.TabGroupUtils;
+import org.chromium.chrome.browser.util.FeatureUtilities;
 import org.chromium.chrome.tab_ui.R;
 import org.chromium.components.feature_engagement.FeatureConstants;
 import org.chromium.ui.modelutil.PropertyKey;
@@ -77,7 +78,7 @@ public class TabListCoordinator implements Destroyable {
      */
     TabListCoordinator(@TabListMode int mode, Context context, TabModelSelector tabModelSelector,
             @Nullable TabListMediator.ThumbnailProvider thumbnailProvider,
-            @Nullable TabListMediator.TitleProvider titleProvider, boolean closeRelatedTabs,
+            @Nullable TabListMediator.TitleProvider titleProvider, boolean actionOnRelatedTabs,
             @Nullable TabListMediator.CreateGroupButtonProvider createGroupButtonProvider,
             @Nullable TabListMediator
                     .GridCardOnClickListenerProvider gridCardOnClickListenerProvider,
@@ -140,18 +141,21 @@ public class TabListCoordinator implements Destroyable {
                 new TabListFaviconProvider(context, Profile.getLastUsedProfile());
 
         mMediator = new TabListMediator(tabListModel, tabModelSelector, thumbnailProvider,
-                titleProvider, tabListFaviconProvider, closeRelatedTabs, createGroupButtonProvider,
-                gridCardOnClickListenerProvider, componentName);
+                titleProvider, tabListFaviconProvider, actionOnRelatedTabs,
+                createGroupButtonProvider, gridCardOnClickListenerProvider, componentName);
 
         if (mMode == TabListMode.GRID) {
             ItemTouchHelper touchHelper = new ItemTouchHelper(mMediator.getItemTouchHelperCallback(
-                    context.getResources().getDimension(R.dimen.swipe_to_dismiss_threshold)));
+                    context.getResources().getDimension(R.dimen.swipe_to_dismiss_threshold),
+                    context.getResources().getDimension(R.dimen.tab_grid_merge_threshold),
+                    !FeatureUtilities.isTabGroupsAndroidEnabled()
+                            || FeatureUtilities.isTabGroupsAndroidUiImprovementsEnabled()));
             touchHelper.attachToRecyclerView(mRecyclerView);
             mMediator.registerOrientationListener(
                     (GridLayoutManager) mRecyclerView.getLayoutManager());
         }
 
-        if (closeRelatedTabs) {
+        if (actionOnRelatedTabs) {
             // Only do this for Grid Tab Switcher.
             // TODO(crbug.com/964406): unregister the listener when we don't need it.
             mRecyclerView.getViewTreeObserver().addOnGlobalLayoutListener(

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

@@ -6,11 +6,16 @@ package org.chromium.chrome.browser.tasks.tab_management;
 
 import static org.chromium.chrome.browser.tasks.tab_management.TabProperties.TAB_ID;
 
+import android.util.Pair;
+
+import org.chromium.chrome.browser.tab.Tab;
 import org.chromium.chrome.browser.tabmodel.TabModel;
 import org.chromium.ui.modelutil.PropertyKey;
 import org.chromium.ui.modelutil.PropertyListModel;
 import org.chromium.ui.modelutil.PropertyModel;
 
+import java.util.List;
+
 /**
  * A {@link PropertyListModel} implementation to keep information about a list of
  * {@link org.chromium.chrome.browser.tab.Tab}s.
@@ -27,4 +32,77 @@ class TabListModel extends PropertyListModel<PropertyModel, PropertyKey> {
         }
         return TabModel.INVALID_TAB_INDEX;
     }
+
+    /**
+     * Sync the {@link TabListModel} with updated information. Update tab id of
+     * the item in {@code index} with the current selected {@code tab} of the group.
+     * @param selectedTab   The current selected tab in the group.
+     * @param index         The index of the item in {@link TabListModel} that needs to be updated.
+     */
+    void updateTabListModelIdForGroup(Tab selectedTab, int index) {
+        get(index).set(TabProperties.TAB_ID, selectedTab.getId());
+    }
+
+    /**
+     * This method gets indexes in the {@link TabListModel} of the two tabs that are merged into one
+     * group.
+     * @param tabModel   The tabModel that owns the tabs.
+     * @param tabs       The list that contains tabs of the newly merged group.
+     * @return A Pair with its first member as the index of the tab that is selected to merge and
+     * the second member as the index of the tab that is being merged into.
+     */
+    Pair<Integer, Integer> getIndexesForMergeToGroup(TabModel tabModel, List<Tab> tabs) {
+        int desIndex = TabModel.INVALID_TAB_INDEX;
+        int srcIndex = TabModel.INVALID_TAB_INDEX;
+        int lastTabModelIndex = tabModel.indexOf(tabs.get(tabs.size() - 1));
+        for (int i = lastTabModelIndex; i >= 0; i--) {
+            Tab curTab = tabModel.getTabAt(i);
+            if (!tabs.contains(curTab)) break;
+            int index = indexFromId(curTab.getId());
+            if (index != TabModel.INVALID_TAB_INDEX && srcIndex == TabModel.INVALID_TAB_INDEX) {
+                srcIndex = index;
+            } else if (index != TabModel.INVALID_TAB_INDEX
+                    && desIndex == TabModel.INVALID_TAB_INDEX) {
+                desIndex = index;
+            }
+        }
+        return new Pair<>(desIndex, srcIndex);
+    }
+
+    /**
+     * This method updates the information in {@link TabListModel} of the selected tab when a merge
+     * related operation happens.
+     * @param index         The index of the item in {@link TabListModel} that needs to be updated.
+     * @param isSelected    Whether the tab is selected or not in a merge related operation. If
+     *         selected, update the corresponding item in {@link TabListModel} to the selected
+     *         state. If not, restore it to original state.
+     */
+    void updateSelectedTabForMergeToGroup(int index, boolean isSelected) {
+        int status = isSelected ? TabListRecyclerView.ANIMATION_STATUS_ZOOM_IN
+                                : TabListRecyclerView.ANIMATION_STATUS_ZOOM_OUT;
+        if (index < 0 || index >= size()
+                || get(index).get(TabProperties.CARD_ANIMATION_STATUS) == status)
+            return;
+
+        get(index).set(TabProperties.CARD_ANIMATION_STATUS, status);
+        get(index).set(TabProperties.ALPHA, isSelected ? 0.8f : 1f);
+    }
+
+    /**
+     * This method updates the information in {@link TabListModel} of the hovered tab when a merge
+     * related operation happens.
+     * @param index         The index of the item in {@link TabListModel} that needs to be updated.
+     * @param isHovered     Whether the tab is hovered or not in a merge related operation. If
+     *         hovered, update the corresponding item in {@link TabListModel} to the hovered state.
+     *         If not, restore it to original state.
+     */
+    void updateHoveredTabForMergeToGroup(int index, boolean isHovered) {
+        int status = isHovered ? TabListRecyclerView.ANIMATION_STATUS_ZOOM_IN
+                               : TabListRecyclerView.ANIMATION_STATUS_ZOOM_OUT;
+        if (index < 0 || index >= size()
+                || get(index).get(TabProperties.CARD_ANIMATION_STATUS) == status)
+            return;
+
+        get(index).set(TabProperties.CARD_ANIMATION_STATUS, status);
+    }
 }

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

@@ -6,6 +6,7 @@ package org.chromium.chrome.browser.tasks.tab_management;
 
 import android.animation.Animator;
 import android.animation.AnimatorListenerAdapter;
+import android.animation.AnimatorSet;
 import android.animation.ObjectAnimator;
 import android.animation.ValueAnimator;
 import android.annotation.SuppressLint;
@@ -28,6 +29,10 @@ import org.chromium.ui.resources.dynamics.ViewResourceAdapter;
  */
 class TabListRecyclerView extends RecyclerView {
     public static final long BASE_ANIMATION_DURATION_MS = 218;
+    public static final long RESTORE_ANIMATION_DURATION_MS = 10;
+    public static final int ANIMATION_STATUS_RESTORE = 0;
+    public static final int ANIMATION_STATUS_ZOOM_OUT = 1;
+    public static final int ANIMATION_STATUS_ZOOM_IN = 2;
 
     /**
      * Field trial parameter for downsampling scaling factor.
@@ -235,4 +240,46 @@ class TabListRecyclerView extends RecyclerView {
         rect.bottom -= loc[1];
         return rect;
     }
+
+    static void scaleTabGridCardView(View view, int status) {
+        AnimatorSet scaleAnimator = new AnimatorSet();
+        float scale = status == ANIMATION_STATUS_ZOOM_IN ? 0.8f : 1f;
+        ObjectAnimator scaleX = ObjectAnimator.ofFloat(view, "scaleX", scale);
+        ObjectAnimator scaleY = ObjectAnimator.ofFloat(view, "scaleY", scale);
+        scaleX.setDuration(status == ANIMATION_STATUS_RESTORE ? RESTORE_ANIMATION_DURATION_MS
+                                                              : BASE_ANIMATION_DURATION_MS);
+        scaleY.setDuration(status == ANIMATION_STATUS_RESTORE ? RESTORE_ANIMATION_DURATION_MS
+                                                              : BASE_ANIMATION_DURATION_MS);
+        scaleAnimator.play(scaleX).with(scaleY);
+        scaleAnimator.start();
+    }
+
+    /**
+     * This method finds out the index of the hovered tab's viewHolder in {@code recyclerView}.
+     * @param recyclerView   The recyclerview that owns the tabs' viewHolders.
+     * @param view           The view of the selected tab.
+     * @param dX             The X offset of the selected tab.
+     * @param dY             The Y offset of the selected tab.
+     * @param threshold      The threshold to judge whether two tabs are overlapped.
+     * @return The index of the hovered tab.
+     */
+    static int getHoveredTabIndex(
+            RecyclerView recyclerView, View view, float dX, float dY, float threshold) {
+        for (int i = 0; i < recyclerView.getChildCount(); i++) {
+            View child = recyclerView.getChildAt(i);
+            if (child.getLeft() == view.getLeft() && child.getTop() == view.getTop()) {
+                continue;
+            }
+            if (isOverlap(child.getLeft(), child.getTop(), view.getLeft() + dX, view.getTop() + dY,
+                        threshold)) {
+                return i;
+            }
+        }
+        return -1;
+    }
+
+    private static boolean isOverlap(
+            float left1, float top1, float left2, float top2, float threshold) {
+        return Math.abs(left1 - left2) < threshold && Math.abs(top1 - top2) < threshold;
+    }
 }

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

@@ -8,7 +8,6 @@ import android.graphics.drawable.Drawable;
 
 import org.chromium.ui.modelutil.PropertyKey;
 import org.chromium.ui.modelutil.PropertyModel;
-import org.chromium.ui.modelutil.PropertyModel.ReadableIntPropertyKey;
 import org.chromium.ui.modelutil.PropertyModel.WritableBooleanPropertyKey;
 import org.chromium.ui.modelutil.PropertyModel.WritableObjectPropertyKey;
 
@@ -16,7 +15,8 @@ import org.chromium.ui.modelutil.PropertyModel.WritableObjectPropertyKey;
  * List of properties to designate information about a single tab.
  */
 public class TabProperties {
-    public static final PropertyModel.ReadableIntPropertyKey TAB_ID = new ReadableIntPropertyKey();
+    public static final PropertyModel.WritableIntPropertyKey TAB_ID =
+            new PropertyModel.WritableIntPropertyKey();
 
     public static final WritableObjectPropertyKey<TabListMediator.TabActionListener>
             TAB_SELECTED_LISTENER = new WritableObjectPropertyKey<>();
@@ -45,9 +45,12 @@ public class TabProperties {
     public static final PropertyModel.WritableFloatPropertyKey ALPHA =
             new PropertyModel.WritableFloatPropertyKey();
 
+    public static final PropertyModel.WritableIntPropertyKey CARD_ANIMATION_STATUS =
+            new PropertyModel.WritableIntPropertyKey();
+
     public static final PropertyKey[] ALL_KEYS_TAB_GRID = new PropertyKey[] {TAB_ID,
             TAB_SELECTED_LISTENER, TAB_CLOSED_LISTENER, FAVICON, THUMBNAIL_FETCHER, IPH_PROVIDER,
-            TITLE, IS_SELECTED, IS_HIDDEN, CREATE_GROUP_LISTENER, ALPHA};
+            TITLE, IS_SELECTED, IS_HIDDEN, CREATE_GROUP_LISTENER, ALPHA, CARD_ANIMATION_STATUS};
 
     public static final PropertyKey[] ALL_KEYS_TAB_STRIP = new PropertyKey[] {
             TAB_ID, TAB_SELECTED_LISTENER, TAB_CLOSED_LISTENER, FAVICON, IS_SELECTED, TITLE};

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

@@ -24,6 +24,7 @@ import android.graphics.Color;
 import android.graphics.drawable.ColorDrawable;
 import android.graphics.drawable.Drawable;
 import android.support.v7.widget.RecyclerView;
+import android.support.v7.widget.helper.ItemTouchHelper;
 import android.view.View;
 
 import org.junit.After;
@@ -89,6 +90,8 @@ public class TabListMediatorUnitTest {
     @Mock
     RecyclerView mRecyclerView;
     @Mock
+    RecyclerView.Adapter mAdapter;
+    @Mock
     TabGroupModelFilter mTabGroupModelFilter;
     @Mock
     EmptyTabModelFilter mEmptyTabModelFilter;
@@ -225,7 +228,8 @@ public class TabListMediatorUnitTest {
 
         doReturn(mEmptyTabModelFilter).when(mTabModelFilterProvider).getCurrentTabModelFilter();
 
-        mMediator.getItemTouchHelperCallback(0f).onMove(mRecyclerView, mViewHolder1, mViewHolder2);
+        mMediator.getItemTouchHelperCallback(0f, 0f, true)
+                .onMove(mRecyclerView, mViewHolder1, mViewHolder2);
 
         verify(mTabModel).moveTab(eq(TAB1_ID), eq(2));
     }
@@ -233,11 +237,13 @@ public class TabListMediatorUnitTest {
     @Test
     public void sendsMoveTabSignalCorrectlyWithGroup() {
         initAndAssertAllProperties();
+        TabGridItemTouchHelperCallback itemTouchHelperCallback =
+                (TabGridItemTouchHelperCallback) mMediator.getItemTouchHelperCallback(0f, 0f, true);
+        itemTouchHelperCallback.setActionsOnAllRelatedTabsForTest(true);
 
-        mMediator.setCloseAllRelatedTabs(true);
         doReturn(mTabGroupModelFilter).when(mTabModelFilterProvider).getCurrentTabModelFilter();
 
-        mMediator.getItemTouchHelperCallback(0f).onMove(mRecyclerView, mViewHolder1, mViewHolder2);
+        itemTouchHelperCallback.onMove(mRecyclerView, mViewHolder1, mViewHolder2);
 
         verify(mTabGroupModelFilter).moveRelatedTabs(eq(TAB1_ID), eq(2));
     }
@@ -248,11 +254,32 @@ public class TabListMediatorUnitTest {
 
         doReturn(mTabGroupModelFilter).when(mTabModelFilterProvider).getCurrentTabModelFilter();
 
-        mMediator.getItemTouchHelperCallback(0f).onMove(mRecyclerView, mViewHolder1, mViewHolder2);
+        mMediator.getItemTouchHelperCallback(0f, 0f, true)
+                .onMove(mRecyclerView, mViewHolder1, mViewHolder2);
 
         verify(mTabModel).moveTab(eq(TAB1_ID), eq(2));
     }
 
+    @Test
+    public void sendsMergeTabSignalCorrectly() {
+        initAndAssertAllProperties();
+        mMediator.setActionOnAllRelatedTabsForTest(true);
+        TabGridItemTouchHelperCallback itemTouchHelperCallback =
+                (TabGridItemTouchHelperCallback) mMediator.getItemTouchHelperCallback(0f, 0f, true);
+        itemTouchHelperCallback.setActionsOnAllRelatedTabsForTest(true);
+        itemTouchHelperCallback.setHoveredTabIndexForTest(POSITION1);
+        itemTouchHelperCallback.setSelectedTabIndexForTest(POSITION2);
+        itemTouchHelperCallback.getMovementFlags(mRecyclerView, mViewHolder1);
+
+        doReturn(mTabGroupModelFilter).when(mTabModelFilterProvider).getCurrentTabModelFilter();
+        doReturn(mAdapter).when(mRecyclerView).getAdapter();
+
+        // Simulate the drop action.
+        itemTouchHelperCallback.onSelectedChanged(mViewHolder1, ItemTouchHelper.ACTION_STATE_IDLE);
+
+        verify(mTabGroupModelFilter).mergeTabsToGroup(eq(TAB2_ID), eq(TAB1_ID));
+    }
+
     @Test
     public void tabClosure() {
         initAndAssertAllProperties();
@@ -277,7 +304,7 @@ public class TabListMediatorUnitTest {
     @Test
     public void tabAddition_GTS() {
         initAndAssertAllProperties();
-        mMediator.setCloseAllRelatedTabsForTest(true);
+        mMediator.setActionOnAllRelatedTabsForTest(true);
 
         Tab newTab = prepareTab(TAB3_ID, TAB3_TITLE);
         doReturn(mTab1).when(mTabModelFilter).getTabAt(0);
@@ -298,7 +325,7 @@ public class TabListMediatorUnitTest {
     @Test
     public void tabAddition_GTS_Skip() {
         initAndAssertAllProperties();
-        mMediator.setCloseAllRelatedTabsForTest(true);
+        mMediator.setActionOnAllRelatedTabsForTest(true);
 
         // Add a new tab to the group with mTab2.
         Tab newTab = prepareTab(TAB3_ID, TAB3_TITLE);
@@ -317,7 +344,7 @@ public class TabListMediatorUnitTest {
     @Test
     public void tabAddition_GTS_Middle() {
         initAndAssertAllProperties();
-        mMediator.setCloseAllRelatedTabsForTest(true);
+        mMediator.setActionOnAllRelatedTabsForTest(true);
 
         Tab newTab = prepareTab(TAB3_ID, TAB3_TITLE);
         doReturn(mTab1).when(mTabModelFilter).getTabAt(0);
@@ -398,6 +425,34 @@ public class TabListMediatorUnitTest {
         assertThat(mModel.get(2).get(TabProperties.TITLE), equalTo(TAB3_TITLE));
     }
 
+    @Test
+    public void tabMergeIntoGroup() {
+        setUpForTabGroupOperation();
+        mMediator.setActionOnAllRelatedTabsForTest(true);
+
+        // Assume that moveTab in TabModel is finished.
+        doReturn(mTab1).when(mTabModel).getTabAt(POSITION2);
+        doReturn(mTab2).when(mTabModel).getTabAt(POSITION1);
+        doReturn(mTabGroupModelFilter).when(mTabModelFilterProvider).getCurrentTabModelFilter();
+
+        // Assume that reset in TabGroupModelFilter is finished.
+        doReturn(new ArrayList<>(Arrays.asList(mTab1, mTab2)))
+                .when(mTabGroupModelFilter)
+                .getRelatedTabList(TAB1_ID);
+
+        assertThat(mModel.size(), equalTo(2));
+        assertThat(mModel.get(1).get(TabProperties.TAB_ID), equalTo(TAB2_ID));
+        assertThat(mModel.get(1).get(TabProperties.TITLE), equalTo(TAB2_TITLE));
+        assertThat(mModel.indexFromId(TAB1_ID), equalTo(POSITION1));
+        assertThat(mModel.indexFromId(TAB2_ID), equalTo(POSITION2));
+
+        mTabGroupModelFilterObserverCaptor.getValue().didMergeTabToGroup(mTab1, TAB2_ID);
+
+        assertThat(mModel.size(), equalTo(1));
+        assertThat(mModel.get(0).get(TabProperties.TAB_ID), equalTo(TAB2_ID));
+        assertThat(mModel.get(0).get(TabProperties.TITLE), equalTo(TAB2_TITLE));
+    }
+
     @Test
     public void tabMovementWithoutGroup_Forward() {
         initAndAssertAllProperties();
@@ -585,8 +640,8 @@ public class TabListMediatorUnitTest {
 
         mMediator = new TabListMediator(mModel, mTabModelSelector,
                 mTabContentManager::getTabThumbnailWithCallback, null, mTabListFaviconProvider,
-                false, null, null, getClass().getSimpleName());
+                true, null, null, getClass().getSimpleName());
 
         initAndAssertAllProperties();
     }
-}
+}
\ No newline at end of file

chrome/android/java/src/org/chromium/chrome/browser/toolbar/TabCountProvider.java

@@ -13,6 +13,7 @@ import org.chromium.chrome.browser.tabmodel.TabModel;
 import org.chromium.chrome.browser.tabmodel.TabModelObserver;
 import org.chromium.chrome.browser.tabmodel.TabModelSelector;
 import org.chromium.chrome.browser.tabmodel.TabModelSelectorObserver;
+import org.chromium.chrome.browser.tasks.tabgroup.TabGroupModelFilter;
 
 import java.util.List;
 
@@ -39,6 +40,11 @@ public class TabCountProvider {
     /** The {@link TabModelObserver} that observes when the tab count may have changed. */
     private TabModelObserver mTabModelFilterObserver;
 
+    /**
+     * The {@link TabGroupModelFilter.Observer} that observes when the tab count may have changed.
+     */
+    private TabGroupModelFilter.Observer mTabGroupModelFilterObserver;
+
     private int mTabCount;
 
     private boolean mIsIncognito;
@@ -136,6 +142,28 @@ public class TabCountProvider {
 
         mTabModelSelector.getTabModelFilterProvider().addTabModelFilterObserver(
                 mTabModelFilterObserver);
+
+        mTabGroupModelFilterObserver = new TabGroupModelFilter.Observer() {
+            @Override
+            public void didMergeTabToGroup(Tab movedTab, int selectedTabIdInGroup) {
+                updateTabCount();
+            }
+
+            @Override
+            public void didMoveTabGroup(Tab movedTab, int tabModelOldIndex, int tabModelNewIndex) {}
+
+            @Override
+            public void didMoveWithinGroup(
+                    Tab movedTab, int tabModelOldIndex, int tabModelNewIndex) {}
+        };
+
+        if (mTabModelSelector.getTabModelFilterProvider().getCurrentTabModelFilter()
+                        instanceof TabGroupModelFilter) {
+            ((TabGroupModelFilter) mTabModelSelector.getTabModelFilterProvider()
+                            .getCurrentTabModelFilter())
+                    .addTabGroupObserver(mTabGroupModelFilterObserver);
+        }
+
         updateTabCount();
     }
 
@@ -148,6 +176,14 @@ public class TabCountProvider {
                     mTabModelFilterObserver);
         }
 
+        if (mTabGroupModelFilterObserver != null
+                && mTabModelSelector.getTabModelFilterProvider().getCurrentTabModelFilter()
+                                instanceof TabGroupModelFilter) {
+            ((TabGroupModelFilter) mTabModelSelector.getTabModelFilterProvider()
+                            .getCurrentTabModelFilter())
+                    .removeTabGroupObserver(mTabGroupModelFilterObserver);
+        }
+
         if (mTabModelSelector != null) {
             mTabModelSelector.removeObserver(mTabModelSelectorObserver);
             mTabModelSelector = null;

tools/metrics/actions/actions.xml

@@ -6050,6 +6050,15 @@ should be able to be added at any place in this file.
   </description>
 </action>
 
+<action name="GridTabSwitcher.DropTabToMerge">
+  <owner>yusufo@chromium.org</owner>
+  <owner>wychen@chromium.org</owner>
+  <description>
+    User drags a tab and drops it on another tab to form a group in grid tab
+    switcher.
+  </description>
+</action>
+
 <action name="GridTabSwitcher.UndoCloseTabGroup">
   <owner>yusufo@chromium.org</owner>
   <owner>wychen@chromium.org</owner>
@@ -20630,6 +20639,12 @@ should be able to be added at any place in this file.
   <description>Please enter the description of this user action.</description>
 </action>
 
+<action name="TabGrid.DragToReorder">
+  <owner>yusufo@chromium.org</owner>
+  <owner>wychen@chromium.org</owner>
+  <description>User drags a tab to reorder it.</description>
+</action>
+
 <action name="TabGridSheet.UndoCloseTab">
   <owner>yusufo@chromium.org</owner>
   <owner>wychen@chromium.org</owner>
@@ -22156,4 +22171,14 @@ should be able to be added at any place in this file.
   <affected-action name="MobileStackViewSwipeCloseTab"/>
 </action-suffix>
 
+<action-suffix separator="." ordering="suffix">
+  <suffix name="GridTabSwitcher"
+      label="Users drag to reorder tabs in grid layout TabSwitcher."/>
+  <suffix name="TabGridDialog"
+      label="Users drag to reorder tabs in tab grid dialog."/>
+  <suffix name="TabGridSheet"
+      label="Users drag to reorder tabs in tab group bottom sheet."/>
+  <affected-action name="TabGrid.DragToReorder"/>
+</action-suffix>
+
 </actions>