Add PriorityDataSourceFactory

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=149543747

library/src/main/java/com/google/android/exoplayer2/upstream/PriorityDataSourceFactory.java

+/*
+ * Copyright (C) 2017 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.google.android.exoplayer2.upstream;
+
+import com.google.android.exoplayer2.upstream.DataSource.Factory;
+import com.google.android.exoplayer2.util.PriorityTaskManager;
+
+/**
+ * A {@link DataSource.Factory} that produces {@link PriorityDataSource} instances.
+ */
+public final class PriorityDataSourceFactory implements Factory {
+
+  private final Factory upstreamFactory;
+  private final PriorityTaskManager priorityTaskManager;
+  private final int priority;
+
+  /**
+   * @param upstreamFactory A {@link DataSource.Factory} to be used to create an upstream {@link
+   *     DataSource} for {@link PriorityDataSource}.
+   * @param priorityTaskManager The priority manager to which PriorityDataSource task is registered.
+   * @param priority The priority of PriorityDataSource task.
+   */
+  public PriorityDataSourceFactory(Factory upstreamFactory, PriorityTaskManager priorityTaskManager,
+      int priority) {
+    this.upstreamFactory = upstreamFactory;
+    this.priorityTaskManager = priorityTaskManager;
+    this.priority = priority;
+  }
+
+  @Override
+  public PriorityDataSource createDataSource() {
+    return new PriorityDataSource(upstreamFactory.createDataSource(), priorityTaskManager,
+        priority);
+  }
+
+}