Add vector_math::FMUL. Replace audio_util::AdjustVolume.

media/base/audio_bus.cc

Index: media/base/audio_bus.cc
diff --git a/media/base/audio_bus.cc b/media/base/audio_bus.cc
index 0dc3300b8defc9e3964555df11d049e8892715ab..850ab3111a446954575c59729e1604b98aec8da3 100644
--- a/media/base/audio_bus.cc
+++ b/media/base/audio_bus.cc
@@ -9,6 +9,7 @@
 #include "base/logging.h"
 #include "media/audio/audio_parameters.h"
 #include "media/base/limits.h"
+#include "media/base/vector_math.h"
 
 namespace media {
 
@@ -307,4 +308,13 @@ void AudioBus::CopyTo(AudioBus* dest) const {
     memcpy(dest->channel(i), channel(i), sizeof(*channel(i)) * frames());
 }
 
+void AudioBus::AdjustVolume(float volume) {
+  if (volume > 0 && volume < 1) {

[Chris Rogers, 2013/04/05 21:31:35]

I would suggest generalizing it by calling is Scale() and removing the < 1
restriction (you can still optimize for the==1 case.  It's valid to want to
scale >1 and even <0 (for phase inversion).

I know right now we're using it in  a specific use case for <audio> (and
similar) where volume must be 0<=volume<=1 but the general case is also useful.

Perhaps we can keep the AdjustVolume() method with these limits and implement it
in terms of another AudioBus method called Scale() which does not have these
limits - WDYT?

[DaleCurtis, 2013/04/05 23:52:30]

Lets see if we can get away with just the Scale() method for now. 
AudioRendererHost::OnSetVolume doesn't except volume ranges outside of [0, 1],
so we should be fine.

+    for (int i = 0; i < channels(); ++i)
+      vector_math::FMUL(channel(i), volume, frames(), channel(i));
+  } else if (volume == 0) {
+    Zero();
+  }
+}
+
 }  // namespace media