Add fake chunk source.

This chunk source retuns SimpleSampleMediaChunks based on the data definition
of a FakeAdaptiveDataSet.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=162351688

testutils/src/main/java/com/google/android/exoplayer2/testutil/FakeChunkSource.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.testutil;
+
+import android.net.Uri;
+import com.google.android.exoplayer2.Format;
+import com.google.android.exoplayer2.source.chunk.Chunk;
+import com.google.android.exoplayer2.source.chunk.ChunkHolder;
+import com.google.android.exoplayer2.source.chunk.ChunkSource;
+import com.google.android.exoplayer2.source.chunk.MediaChunk;
+import com.google.android.exoplayer2.source.chunk.SingleSampleMediaChunk;
+import com.google.android.exoplayer2.testutil.FakeDataSet.FakeData.Segment;
+import com.google.android.exoplayer2.trackselection.TrackSelection;
+import com.google.android.exoplayer2.upstream.DataSource;
+import com.google.android.exoplayer2.upstream.DataSpec;
+import com.google.android.exoplayer2.util.MimeTypes;
+import java.io.IOException;
+import java.util.List;
+
+/**
+ * Fake {@link ChunkSource} with adaptive media chunks of a given duration.
+ */
+public final class FakeChunkSource implements ChunkSource {
+
+  /**
+   * Factory for a {@link FakeChunkSource}.
+   */
+  public static final class Factory {
+
+    private final FakeAdaptiveDataSet.Factory dataSetFactory;
+    private final FakeDataSource.Factory dataSourceFactory;
+
+    public Factory(FakeAdaptiveDataSet.Factory dataSetFactory,
+        FakeDataSource.Factory dataSourceFactory) {
+      this.dataSetFactory = dataSetFactory;
+      this.dataSourceFactory = dataSourceFactory;
+    }
+
+    public FakeChunkSource createChunkSource(TrackSelection trackSelection, long durationUs) {
+      FakeAdaptiveDataSet dataSet = dataSetFactory.createDataSet(trackSelection, durationUs);
+      dataSourceFactory.setFakeDataSet(dataSet);
+      DataSource dataSource = dataSourceFactory.createDataSource();
+      return new FakeChunkSource(trackSelection, dataSource, dataSet);
+    }
+
+  }
+
+  private final TrackSelection trackSelection;
+  private final DataSource dataSource;
+  private final FakeAdaptiveDataSet dataSet;
+
+  public FakeChunkSource(TrackSelection trackSelection, DataSource dataSource,
+      FakeAdaptiveDataSet dataSet) {
+    this.trackSelection = trackSelection;
+    this.dataSource = dataSource;
+    this.dataSet = dataSet;
+  }
+
+  @Override
+  public void maybeThrowError() throws IOException {
+    // Do nothing.
+  }
+
+  @Override
+  public int getPreferredQueueSize(long playbackPositionUs, List<? extends MediaChunk> queue) {
+    return trackSelection.evaluateQueueSize(playbackPositionUs, queue);
+  }
+
+  @Override
+  public void getNextChunk(MediaChunk previous, long playbackPositionUs, ChunkHolder out) {
+    long bufferedDurationUs = previous != null ? (previous.endTimeUs - playbackPositionUs) : 0;
+    trackSelection.updateSelectedTrack(bufferedDurationUs);
+    int chunkIndex = previous == null ? dataSet.getChunkIndexByPosition(playbackPositionUs)
+        : previous.getNextChunkIndex();
+    if (chunkIndex >= dataSet.getChunkCount()) {
+      out.endOfStream = true;
+    } else {
+      Format selectedFormat = trackSelection.getSelectedFormat();
+      long startTimeUs = dataSet.getStartTime(chunkIndex);
+      long endTimeUs = startTimeUs + dataSet.getChunkDuration(chunkIndex);
+      String uri = dataSet.getUri(trackSelection.getSelectedIndex());
+      Segment fakeDataChunk = dataSet.getData(uri).getSegments().get(chunkIndex);
+      DataSpec dataSpec = new DataSpec(Uri.parse(uri), fakeDataChunk.byteOffset,
+          fakeDataChunk.length, null);
+      int trackType = MimeTypes.getTrackType(selectedFormat.sampleMimeType);
+      out.chunk = new SingleSampleMediaChunk(dataSource, dataSpec, selectedFormat,
+          trackSelection.getSelectionReason(), trackSelection.getSelectionData(), startTimeUs,
+          endTimeUs, chunkIndex, trackType, selectedFormat);
+    }
+  }
+
+  @Override
+  public void onChunkLoadCompleted(Chunk chunk) {
+    // Do nothing.
+  }
+
+  @Override
+  public boolean onChunkLoadError(Chunk chunk, boolean cancelable, Exception e) {
+    return false;
+  }
+
+}