Fix building FFMPEG into Android

media/filters/decoder_selector.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef MEDIA_FILTERS_DECODER_SELECTOR_H_
 #define MEDIA_FILTERS_DECODER_SELECTOR_H_
 
 #include <memory>
 
 #include "base/callback.h"
@@ skipping 61 matching lines @@
   // 3. |cdm_context| is optional. If |cdm_context| is
   //    null, no CDM will be available to perform decryption.
   void SelectDecoder(StreamTraits* traits,
                      DemuxerStream* stream,
                      CdmContext* cdm_context,
                      const SelectDecoderCB& select_decoder_cb,
                      const typename Decoder::OutputCB& output_cb,
                      const base::Closure& waiting_for_decryption_key_cb);
 
  private:
-#if !defined(OS_ANDROID)
+#if !defined(DISABLE_FFMPEG_VIDEO_DECODERS)

[xhwang, 2017/05/01 17:10:00]

I saw this when working on the DecoderSelector and got confused. The previous
defined(OS_ANDROID) check isn't super accurate. It's more like "if not
supporting decrypting decoder in the CDM". This is also checked at run-time, but
excluding it at build time will make things slightly simper/faster (I hope).

So I have a question on https://codereview.chromium.org/2808093008, why do you
want to touch Decrypting*Decoder, when you are trying disable FFmpeg*Decoder?
They are two different decoders...

Could you please 

[kraush, 2017/05/01 18:14:59]

Sorry, just to clarify: Are you saying the changes made to
media/filters/decoder_selector.cc in https://codereview.chromium.org/2808093008
seem incorrect, because ffmpeg flags should not guard decrypting_decoder code?

If so, should we loop in rduszynski@opera.com who made those changes?
I'm unfortunately not sure what build configuration they use and thus why those
changes were made :(

   void InitializeDecryptingDecoder();
   void DecryptingDecoderInitDone(bool success);
 #endif
   void InitializeDecryptingDemuxerStream();
   void DecryptingDemuxerStreamInitDone(PipelineStatus status);
   void InitializeDecoder();
   void DecoderInitDone(bool success);
   void ReturnNullDecoder();
 
   scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
@@ skipping 22 matching lines @@
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(DecoderSelector);
 };
 
 typedef DecoderSelector<DemuxerStream::VIDEO> VideoDecoderSelector;
 typedef DecoderSelector<DemuxerStream::AUDIO> AudioDecoderSelector;
 
 }  // namespace media
 
 #endif  // MEDIA_FILTERS_DECODER_SELECTOR_H_