[chromecast] Slew stream volume changes in StreamMixerAlsa.

chromecast/media/cma/backend/alsa/stream_mixer_alsa.cc

Index: chromecast/media/cma/backend/alsa/stream_mixer_alsa.cc
diff --git a/chromecast/media/cma/backend/alsa/stream_mixer_alsa.cc b/chromecast/media/cma/backend/alsa/stream_mixer_alsa.cc
index 5f4b3e242dba708faca54239b5c517c4d7ebe71d..faf4b5666a81209cb786ce8e98bd04548ca1ccdc 100644
--- a/chromecast/media/cma/backend/alsa/stream_mixer_alsa.cc
+++ b/chromecast/media/cma/backend/alsa/stream_mixer_alsa.cc
@@ -23,7 +23,6 @@
 #include "chromecast/media/cma/backend/alsa/stream_mixer_alsa_input_impl.h"
 #include "media/base/audio_bus.h"
 #include "media/base/media_switches.h"
-#include "media/base/vector_math.h"
 
 #define RETURN_REPORT_ERROR(snd_func, ...)                        \
   do {                                                            \
@@ -830,10 +829,8 @@ bool StreamMixerAlsa::TryWriteFrames() {
   for (InputQueue* input : active_inputs) {
     input->GetResampledData(temp_.get(), chunk_size);
     for (int c = 0; c < kNumOutputChannels; ++c) {
-      float volume_scalar = input->volume_multiplier();
-      DCHECK(volume_scalar >= 0.0 && volume_scalar <= 1.0) << volume_scalar;
-      ::media::vector_math::FMAC(temp_->channel(c), volume_scalar, chunk_size,
-                                 mixed_->channel(c));
+      input->VolumeScaleAccumulate(temp_->channel(c), chunk_size,

[kmackay, 2016/09/15 01:51:36]

does this work properly? seems like it will slew one channel, and then continue
slewing the next channel, and so on (so channel 0 will slew from eg. 0.0 ->
0.05, and channel 1 will slew from 0.05 -> 0.1).

[jyw, 2016/09/15 22:16:23]

Done.

+                                   mixed_->channel(c));
     }
   }