Enable implicit signalling for HE AAC v1 & v2 in ADTS.

media/base/audio_buffer.cc

Index: media/base/audio_buffer.cc
diff --git a/media/base/audio_buffer.cc b/media/base/audio_buffer.cc
index 1ea2363e726b14609721bd436f0bb81906a40277..927c20a6faf73b1634fbada0a092aadb746167ed 100644
--- a/media/base/audio_buffer.cc
+++ b/media/base/audio_buffer.cc
@@ -208,6 +208,12 @@ inline int16_t ConvertSample<float, int16_t>(float sample) {
                            : sample * std::numeric_limits<int16_t>::max()));
 }
 
+void AudioBuffer::AdjustSampleRate(int sample_rate) {
+  sample_rate_ = sample_rate;
+  if (!end_of_stream_)
+    duration_ = CalculateDuration(adjusted_frame_count_, sample_rate_);
+}
+
 void AudioBuffer::ReadFrames(int frames_to_copy,
                              int source_frame_offset,
                              int dest_frame_offset,