Fix for AudioEncoder crash when using cast.streaming API.

media/cast/audio_sender/audio_encoder.cc

 // Copyright 2013 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/cast/audio_sender/audio_encoder.h"
 
 #include <algorithm>
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
@@ skipping 41 matching lines @@
     CHECK_LE(samples_per_10ms_ * num_channels_,
              EncodedAudioFrame::kMaxNumberOfSamples);
   }
 
   virtual ~ImplBase() {}
 
   void EncodeAudio(const AudioBus* audio_bus,
                    const base::TimeTicks& recorded_time,
                    const base::Closure& done_callback) {
     int src_pos = 0;
-    while (src_pos < audio_bus->frames()) {
+    while (audio_bus && src_pos < audio_bus->frames()) {
       const int num_samples_to_xfer =
           std::min(samples_per_10ms_ - buffer_fill_end_,
                    audio_bus->frames() - src_pos);
       DCHECK_EQ(audio_bus->channels(), num_channels_);
       TransferSamplesIntoBuffer(
           audio_bus, src_pos, buffer_fill_end_, num_samples_to_xfer);
       src_pos += num_samples_to_xfer;
       buffer_fill_end_ += num_samples_to_xfer;
 
       if (src_pos == audio_bus->frames()) {
         cast_environment_->PostTask(CastEnvironment::MAIN, FROM_HERE,
                                     done_callback);
-        // Note: |audio_bus| is now invalid..
+        // Note: |audio_bus| is invalid once done_callback is invoked.
+        audio_bus = NULL;
       }
 
       if (buffer_fill_end_ == samples_per_10ms_) {
         scoped_ptr<EncodedAudioFrame> audio_frame(new EncodedAudioFrame());
         audio_frame->codec = codec_;
         audio_frame->frame_id = frame_id_++;
         audio_frame->samples = samples_per_10ms_;
         if (EncodeFromFilledBuffer(&audio_frame->data)) {
           // Compute an offset to determine the recorded time for the first
           // audio sample in the buffer.
@@ skipping 199 matching lines @@
     const base::TimeTicks& recorded_time,
     const base::Closure& done_callback) {
   DCHECK(cast_environment_->CurrentlyOn(CastEnvironment::AUDIO_ENCODER));
   impl_->EncodeAudio(audio_bus, recorded_time, done_callback);
   cast_environment_->PostTask(CastEnvironment::MAIN, FROM_HERE,
       base::Bind(LogAudioEncodedEvent, cast_environment_, recorded_time));
 }
 
 }  // namespace cast
 }  // namespace media