Add filtering manifest parsers for DASH, HLS and SmoothStreaming

These parsers can be used to get a manifest which includes only the
representations identified by the given keys.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=182932874

library/dash/src/main/java/com/google/android/exoplayer2/source/dash/manifest/FilteringDashManifestParser.java

+/*
+ * Copyright (C) 2018 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.source.dash.manifest;
+
+import android.net.Uri;
+import com.google.android.exoplayer2.upstream.ParsingLoadable.Parser;
+import java.io.IOException;
+import java.io.InputStream;
+import java.util.ArrayList;
+
+/**
+ * A parser of media presentation description files which includes only the representations
+ * identified by the given keys.
+ */
+public final class FilteringDashManifestParser implements Parser<DashManifest> {
+
+  private final DashManifestParser dashManifestParser;
+  private final ArrayList<RepresentationKey> filter;
+
+  /** @param filter The representation keys that should be retained in the parsed manifests. */
+  public FilteringDashManifestParser(ArrayList<RepresentationKey> filter) {
+    this.dashManifestParser = new DashManifestParser();
+    this.filter = filter;
+  }
+
+  @Override
+  public DashManifest parse(Uri uri, InputStream inputStream) throws IOException {
+    return dashManifestParser.parse(uri, inputStream).copy(filter);
+  }
+}

library/hls/src/main/java/com/google/android/exoplayer2/source/hls/playlist/FilteringHlsPlaylistParser.java

+/*
+ * Copyright (C) 2018 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.source.hls.playlist;
+
+import android.net.Uri;
+import com.google.android.exoplayer2.upstream.ParsingLoadable.Parser;
+import java.io.IOException;
+import java.io.InputStream;
+import java.util.List;
+
+/** A HLS playlists parser which includes only the renditions identified by the given urls. */
+public final class FilteringHlsPlaylistParser implements Parser<HlsPlaylist> {
+
+  private final HlsPlaylistParser hlsPlaylistParser;
+  private final List<String> filter;
+
+  /** @param filter The urls to renditions that should be retained in the parsed playlists. */
+  public FilteringHlsPlaylistParser(List<String> filter) {
+    this.hlsPlaylistParser = new HlsPlaylistParser();
+    this.filter = filter;
+  }
+
+  @Override
+  public HlsPlaylist parse(Uri uri, InputStream inputStream) throws IOException {
+    HlsPlaylist hlsPlaylist = hlsPlaylistParser.parse(uri, inputStream);
+    HlsMasterPlaylist hlsMasterPlaylist;
+    if (hlsPlaylist instanceof HlsMasterPlaylist) {
+      hlsMasterPlaylist = (HlsMasterPlaylist) hlsPlaylist;
+    } else {
+      hlsMasterPlaylist = HlsMasterPlaylist.createSingleVariantMasterPlaylist(hlsPlaylist.baseUri);
+    }
+    return hlsMasterPlaylist.copy(filter);
+  }
+}

library/smoothstreaming/src/main/java/com/google/android/exoplayer2/source/smoothstreaming/manifest/FilteringSsManifestParser.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.source.smoothstreaming.manifest;
+
+import android.net.Uri;
+import com.google.android.exoplayer2.upstream.ParsingLoadable.Parser;
+import java.io.IOException;
+import java.io.InputStream;
+import java.util.List;
+
+/**
+ * A parser of SmoothStreaming manifest which includes only the tracks identified by the given keys.
+ */
+public final class FilteringSsManifestParser implements Parser<SsManifest> {
+
+  private final SsManifestParser ssManifestParser;
+  private final List<TrackKey> filter;
+
+  /** @param filter The track keys that should be retained in the parsed manifests. */
+  public FilteringSsManifestParser(List<TrackKey> filter) {
+    this.ssManifestParser = new SsManifestParser();
+    this.filter = filter;
+  }
+
+  @Override
+  public SsManifest parse(Uri uri, InputStream inputStream) throws IOException {
+    return ssManifestParser.parse(uri, inputStream).copy(filter);
+  }
+}