Fix the flaky MediaSourcePlayerTest

If seek happens while requesting data for the inactive chunk, the ack for the data request will call OnDecodeCompleted().
However, the decoder job is waiting for the OnDecodeCompleted() from the active chunk.
Tests:We already have seveal tests covering requesting inactive chunk during seek. This CL should fix the flakiness in there.

BUG=361541

Review URL: https://codereview.chromium.org/227523005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@262934 0039d316-1c4b-4281-b951-d872f2087c98

media/base/android/media_decoder_job.cc

@@ -72,13 +72,19 @@ void MediaDecoderJob::OnDataReceived(const DemuxerData& data) {
   is_requesting_demuxer_data_ = false;
 
   base::Closure done_cb = base::ResetAndReturn(&on_data_received_cb_);
+
+  // If this data request is for the inactive chunk, or |on_data_received_cb_|
+  // was set to null by ClearData() or Release(), do nothing.
+  if (done_cb.is_null())
+    return;
+
   if (stop_decode_pending_) {
+    DCHECK(is_decoding());
     OnDecodeCompleted(MEDIA_CODEC_STOPPED, kNoTimestamp(), 0);
     return;
   }
 
-  if (!done_cb.is_null())
-    done_cb.Run();
+  done_cb.Run();
 }
 
 void MediaDecoderJob::Prefetch(const base::Closure& prefetch_cb) {