Fix playback of DASH/VP9/SegmentList DASH content

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=154077149

library/core/src/main/java/com/google/android/exoplayer2/extractor/DefaultExtractorsFactory.java

@@ -64,11 +64,25 @@ public final class DefaultExtractorsFactory implements ExtractorsFactory {
     FLAC_EXTRACTOR_CONSTRUCTOR = flacExtractorConstructor;
   }
 
+  private @MatroskaExtractor.Flags int matroskaFlags;
   private @FragmentedMp4Extractor.Flags int fragmentedMp4Flags;
   private @Mp3Extractor.Flags int mp3Flags;
   private @DefaultTsPayloadReaderFactory.Flags int tsFlags;
 
   /**
+   * Sets flags for {@link MatroskaExtractor} instances created by the factory.
+   *
+   * @see MatroskaExtractor#MatroskaExtractor(int)
+   * @param flags The flags to use.
+   * @return The factory, for convenience.
+   */
+  public synchronized DefaultExtractorsFactory setMatroskaExtractorFlags(
+      @MatroskaExtractor.Flags int flags) {
+    this.matroskaFlags = flags;
+    return this;
+  }
+
+  /**
    * Sets flags for {@link FragmentedMp4Extractor} instances created by the factory.
    *
    * @see FragmentedMp4Extractor#FragmentedMp4Extractor(int)
@@ -110,7 +124,7 @@ public final class DefaultExtractorsFactory implements ExtractorsFactory {
   @Override
   public synchronized Extractor[] createExtractors() {
     Extractor[] extractors = new Extractor[FLAC_EXTRACTOR_CONSTRUCTOR == null ? 11 : 12];
-    extractors[0] = new MatroskaExtractor();
+    extractors[0] = new MatroskaExtractor(matroskaFlags);
     extractors[1] = new FragmentedMp4Extractor(fragmentedMp4Flags);
     extractors[2] = new Mp4Extractor();
     extractors[3] = new Mp3Extractor(mp3Flags);

library/core/src/main/java/com/google/android/exoplayer2/extractor/mkv/MatroskaExtractor.java

@@ -15,6 +15,7 @@
  */
 package com.google.android.exoplayer2.extractor.mkv;
 
+import android.support.annotation.IntDef;
 import android.util.SparseArray;
 import com.google.android.exoplayer2.C;
 import com.google.android.exoplayer2.Format;
@@ -38,6 +39,8 @@ import com.google.android.exoplayer2.util.Util;
 import com.google.android.exoplayer2.video.AvcConfig;
 import com.google.android.exoplayer2.video.HevcConfig;
 import java.io.IOException;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
 import java.nio.ByteBuffer;
 import java.nio.ByteOrder;
 import java.util.ArrayList;
@@ -64,6 +67,22 @@ public final class MatroskaExtractor implements Extractor {
 
   };
 
+  /**
+   * Flags controlling the behavior of the extractor.
+   */
+  @Retention(RetentionPolicy.SOURCE)
+  @IntDef(flag = true, value = {FLAG_DISABLE_SEEK_FOR_CUES})
+  public @interface Flags {}
+  /**
+   * Flag to disable seeking for cues.
+   * <p>
+   * Normally (i.e. when this flag is not set) the extractor will seek to the cues element if its
+   * position is specified in the seek head and if it's after the first cluster. Setting this flag
+   * disables seeking to the cues element. If the cues element is after the first cluster then the
+   * media is treated as being unseekable.
+   */
+  public static final int FLAG_DISABLE_SEEK_FOR_CUES = 1;
+
   private static final int UNSET_ENTRY_ID = -1;
 
   private static final int BLOCK_STATE_START = 0;
@@ -222,6 +241,7 @@ public final class MatroskaExtractor implements Extractor {
   private final EbmlReader reader;
   private final VarintReader varintReader;
   private final SparseArray<Track> tracks;
+  private final boolean seekForCuesEnabled;
 
   // Temporary arrays.
   private final ParsableByteArray nalStartCode;
@@ -289,12 +309,17 @@ public final class MatroskaExtractor implements Extractor {
   private ExtractorOutput extractorOutput;
 
   public MatroskaExtractor() {
-    this(new DefaultEbmlReader());
+    this(0);
+  }
+
+  public MatroskaExtractor(@Flags int flags) {
+    this(new DefaultEbmlReader(), flags);
   }
 
-  /* package */ MatroskaExtractor(EbmlReader reader) {
+  /* package */ MatroskaExtractor(EbmlReader reader, @Flags int flags) {
     this.reader = reader;
     this.reader.init(new InnerEbmlReaderOutput());
+    seekForCuesEnabled = (flags & FLAG_DISABLE_SEEK_FOR_CUES) == 0;
     varintReader = new VarintReader();
     tracks = new SparseArray<>();
     scratch = new ParsableByteArray(4);
@@ -448,7 +473,7 @@ public final class MatroskaExtractor implements Extractor {
       case ID_CLUSTER:
         if (!sentSeekMap) {
           // We need to build cues before parsing the cluster.
-          if (cuesContentPosition != C.POSITION_UNSET) {
+          if (seekForCuesEnabled && cuesContentPosition != C.POSITION_UNSET) {
             // We know where the Cues element is located. Seek to request it.
             seekForCues = true;
           } else {

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

@@ -393,7 +393,7 @@ public class DefaultDashChunkSource implements DashChunkSource {
         if (MimeTypes.APPLICATION_RAWCC.equals(containerMimeType)) {
           extractor = new RawCcExtractor(representation.format);
         } else if (mimeTypeIsWebm(containerMimeType)) {
-          extractor = new MatroskaExtractor();
+          extractor = new MatroskaExtractor(MatroskaExtractor.FLAG_DISABLE_SEEK_FOR_CUES);
         } else {
           int flags = 0;
           if (enableEventMessageTrack) {