Refactor FlacBinarySearchSeeker.

Rewrite FlacBinarySearchSeeker and extract out the core binary search algorithm
into BinarySearchSeeker class so it can be re-used for other formats.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=206012900

extensions/flac/src/androidTest/java/com/google/android/exoplayer2/ext/flac/FlacBinarySearchSeekerTest.java

@@ -67,6 +67,6 @@ public final class FlacBinarySearchSeekerTest extends InstrumentationTestCase {
             decoderJni.decodeMetadata(), /* firstFramePosition= */ 0, data.length, decoderJni);
 
     seeker.setSeekTargetUs(/* timeUs= */ 1000);
-    assertThat(seeker.hasPendingSeek()).isTrue();
+    assertThat(seeker.isSeeking()).isTrue();
   }
 }

extensions/flac/src/main/java/com/google/android/exoplayer2/ext/flac/FlacExtractor.java

@@ -21,6 +21,7 @@ import android.support.annotation.IntDef;
 import android.support.annotation.Nullable;
 import com.google.android.exoplayer2.C;
 import com.google.android.exoplayer2.Format;
+import com.google.android.exoplayer2.extractor.BinarySearchSeeker;
 import com.google.android.exoplayer2.extractor.Extractor;
 import com.google.android.exoplayer2.extractor.ExtractorInput;
 import com.google.android.exoplayer2.extractor.ExtractorOutput;
@@ -52,9 +53,8 @@ public final class FlacExtractor implements Extractor {
   /** Flags controlling the behavior of the extractor. */
   @Retention(RetentionPolicy.SOURCE)
   @IntDef(
-    flag = true,
-    value = {FLAG_DISABLE_ID3_METADATA}
-  )
+      flag = true,
+      value = {FLAG_DISABLE_ID3_METADATA})
   public @interface Flags {}
 
   /**
@@ -79,6 +79,7 @@ public final class FlacExtractor implements Extractor {
 
   private ParsableByteArray outputBuffer;
   private ByteBuffer outputByteBuffer;
+  private BinarySearchSeeker.OutputFrameHolder outputFrameHolder;
   private FlacStreamInfo streamInfo;
 
   private Metadata id3Metadata;
@@ -131,7 +132,7 @@ public final class FlacExtractor implements Extractor {
     decoderJni.setData(input);
     readPastStreamInfo(input);
 
-    if (flacBinarySearchSeeker != null && flacBinarySearchSeeker.hasPendingSeek()) {
+    if (flacBinarySearchSeeker != null && flacBinarySearchSeeker.isSeeking()) {
       return handlePendingSeek(input, seekPosition);
     }
 
@@ -215,6 +216,7 @@ public final class FlacExtractor implements Extractor {
     outputFormat(streamInfo);
     outputBuffer = new ParsableByteArray(streamInfo.maxDecodedFrameSize());
     outputByteBuffer = ByteBuffer.wrap(outputBuffer.data);
+    outputFrameHolder = new BinarySearchSeeker.OutputFrameHolder(outputByteBuffer);
   }
 
   private FlacStreamInfo decodeStreamInfo(ExtractorInput input)
@@ -277,9 +279,10 @@ public final class FlacExtractor implements Extractor {
   private int handlePendingSeek(ExtractorInput input, PositionHolder seekPosition)
       throws InterruptedException, IOException {
     int seekResult =
-        flacBinarySearchSeeker.handlePendingSeek(input, seekPosition, outputByteBuffer);
+        flacBinarySearchSeeker.handlePendingSeek(input, seekPosition, outputFrameHolder);
+    ByteBuffer outputByteBuffer = outputFrameHolder.byteBuffer;
     if (seekResult == RESULT_CONTINUE && outputByteBuffer.limit() > 0) {
-      writeLastSampleToOutput(outputByteBuffer.limit(), decoderJni.getLastFrameTimestamp());
+      writeLastSampleToOutput(outputByteBuffer.limit(), outputFrameHolder.timeUs);
     }
     return seekResult;
   }