Fix incorrect opus seek preroll and flaky pre-skip removal.

media/base/audio_discard_helper.cc

 // 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.
 
 #include "media/base/audio_discard_helper.h"
 
 #include <algorithm>
 
 #include "base/logging.h"
 #include "media/base/audio_buffer.h"
@@ skipping 86 matching lines @@
   if (discard_frames_ > 0) {
     const size_t decoded_frames = decoded_buffer->frame_count();
     const size_t frames_to_discard = std::min(discard_frames_, decoded_frames);
     discard_frames_ -= frames_to_discard;
 
     DVLOG(1) << "Initial discard of " << frames_to_discard << " out of "
              << decoded_frames << " frames.";
 
     // If everything would be discarded, indicate a new buffer is required.
     if (frames_to_discard == decoded_frames) {
-      // For simplicity disallow cases where a buffer with discard padding is
-      // present.  Doing so allows us to avoid complexity around tracking
-      // discards across buffers.
-      DCHECK(current_discard_padding.first == base::TimeDelta());
-      DCHECK(current_discard_padding.second == base::TimeDelta());
+      // For simplicity, we just drop any discard padding if |discard_frames_|
+      // consumes the entire buffer.

[chcunningham, 2015/07/31 19:48:44]

What about the case where current_discard_padding is swapped into
delayed_discard_padding_? Is it right to still use the padding in a delayed
fashion when we would otherwise drop the discard in the not-delayed case?

[DaleCurtis, 2015/08/03 22:49:53]

That would still be correct, as the initial discard only applies to what's
already been decoded; whereas with delayed discard we haven't decoded the next
buffer just yet.

       return false;
     }
 
     decoded_buffer->TrimStart(frames_to_discard);
   }
 
   // Process any delayed end discard from the previous buffer.
   if (delayed_end_discard_ > 0) {
     DCHECK_GT(decoder_delay_, 0u);
 
@@ skipping 110 matching lines @@
     DCHECK(current_discard_padding.second == base::TimeDelta());
   }
 
   // Assign timestamp to the buffer.
   decoded_buffer->set_timestamp(timestamp_helper_.GetTimestamp());
   timestamp_helper_.AddFrames(decoded_buffer->frame_count());
   return true;
 }
 
 }  // namespace media