Folder support in Taskbar

- Add TaskbarActivityContext which allows shared Launcher elements to
  "just work" using existing generic ActivityContext.
- TaskbarContainerView extends BaseDragLayer<TaskbarActivityContext>.
- Inflate FolderIcon and Folder using TaskbarActivityContext to be
  shown in TaskbarContainerView.
- Use TaskbarActivityContext's DeviceProfile to determine icon size
  instead of overriding in styles. This also ensures that normal
  BubbleTextView icons have the same size as FolderIcons.

Test: Place a folder in home screen hotseat, ensure it shows up in
taskbar and can be opened, and that apps inside it can be launched
or dragged.
Bug: 171917176

Change-Id: Ic25d2f84bcd7e3399c88989305ea565497c030d9

quickstep/src/com/android/launcher3/taskbar/TaskbarActivityContext.java

@@ -0,0 +1,78 @@
+/*
+ * Copyright (C) 2021 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.android.launcher3.taskbar;
+
+import android.content.ContextWrapper;
+import android.graphics.Rect;
+import android.view.LayoutInflater;
+
+import com.android.launcher3.BaseQuickstepLauncher;
+import com.android.launcher3.DeviceProfile;
+import com.android.launcher3.R;
+import com.android.launcher3.views.ActivityContext;
+import com.android.launcher3.views.BaseDragLayer;
+
+/**
+ * The {@link ActivityContext} with which we inflate Taskbar-related Views. This allows UI elements
+ * that are used by both Launcher and Taskbar (such as Folder) to reference a generic
+ * ActivityContext and BaseDragLayer instead of the Launcher activity and its DragLayer.
+ */
+public class TaskbarActivityContext extends ContextWrapper implements ActivityContext {
+
+    private final DeviceProfile mDeviceProfile;
+    private final LayoutInflater mLayoutInflater;
+    private final TaskbarContainerView mTaskbarContainerView;
+
+    public TaskbarActivityContext(BaseQuickstepLauncher launcher) {
+        super(launcher);
+        mDeviceProfile = launcher.getDeviceProfile().copy(this);
+        float taskbarIconSize = getResources().getDimension(R.dimen.taskbar_icon_size);
+        float iconScale = taskbarIconSize / mDeviceProfile.iconSizePx;
+        mDeviceProfile.updateIconSize(iconScale, getResources());
+
+        mLayoutInflater = LayoutInflater.from(this).cloneInContext(this);
+
+        mTaskbarContainerView = (TaskbarContainerView) mLayoutInflater
+                .inflate(R.layout.taskbar, null, false);
+    }
+
+    public TaskbarContainerView getTaskbarContainerView() {
+        return mTaskbarContainerView;
+    }
+
+    /**
+     * @return A LayoutInflater to use in this Context. Views inflated with this LayoutInflater will
+     * be able to access this TaskbarActivityContext via ActivityContext.lookupContext().
+     */
+    public LayoutInflater getLayoutInflater() {
+        return mLayoutInflater;
+    }
+
+    @Override
+    public BaseDragLayer<TaskbarActivityContext> getDragLayer() {
+        return mTaskbarContainerView;
+    }
+
+    @Override
+    public DeviceProfile getDeviceProfile() {
+        return mDeviceProfile;
+    }
+
+    @Override
+    public Rect getFolderBoundingBox() {
+        return mTaskbarContainerView.getFolderBoundingBox();
+    }
+}