Removed WallpaperController dependency on WindowList.

WallpaperController now accesses the container hierarchy directly
to determine the state of the wallpaper windows and targets.

Bug: 30060889
Test: cts/hostsidetests/services/activityandwindowmanager/util/run-test \
      android.server.cts.ActivityManagerTransitionSelectionTests

Change-Id: Ib70beaf340f257ad4e1093cc127f81e7adf41636

core/java/com/android/internal/util/ToBooleanFunction.java

@@ -0,0 +1,43 @@
+/*
+ * Copyright (C) 2016 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.internal.util;
+
+import java.util.function.Function;
+
+/**
+ * Represents a function that produces an boolean-valued result.  This is the
+ * {@code boolean}-producing primitive specialization for {@link Function}.
+ *
+ * <p>This is a <a href="package-summary.html">functional interface</a>
+ * whose functional method is {@link #apply(Object)}.
+ *
+ * @param <T> the type of the input to the function
+ *
+ * @see Function
+ * @since 1.8
+ */
+@FunctionalInterface
+public interface ToBooleanFunction<T> {
+
+    /**
+     * Applies this function to the given argument.
+     *
+     * @param value the function argument
+     * @return the function result
+     */
+    boolean apply(T value);
+}