Fix wrong timing when audio is muted.

media/audio/audio_util.cc

 // Copyright (c) 2012 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.
 
 // Software adjust volume of samples, allows each audio stream its own
 // volume without impacting master volume for chrome and other applications.
 
 // Implemented as templates to allow 8, 16 and 32 bit implementations.
 // 8 bit is unsigned and biased by 128.
 
@@ skipping 242 matching lines @@
       else if (sample < min_value)
         sample = min_value;
 
       destination[j * channels + i] = static_cast<Format>(sample) + bias;
     }
   }
 }
 
 void InterleaveFloatToInt(const std::vector<float*>& source, void* dst,
                           size_t number_of_frames, int bytes_per_sample) {
-  switch(bytes_per_sample) {
+  switch (bytes_per_sample) {
     case 1:
       InterleaveFloatToInt<uint8, int32>(source, dst, number_of_frames);
       break;
     case 2:
       InterleaveFloatToInt<int16, int32>(source, dst, number_of_frames);
       break;
     case 4:
       InterleaveFloatToInt<int32, int64>(source, dst, number_of_frames);
       break;
     default:
       break;
   }
 }
 
 // TODO(enal): use template specialization and size-specific intrinsics.
 //             Call is on the time-critical path, and by using SSE/AVX
 //             instructions we can speed things up by ~4-8x, more for the case
 //             when we have to adjust volume as well.
 template<class Format, class Fixed, int min_value, int max_value, int bias>
 static void MixStreams(Format* dst, Format* src, int count, float volume) {
+  if (volume == 0.0f)
+    return;
   if (volume == 1.0f) {
     // Most common case -- no need to adjust volume.
     for (int i = 0; i < count; ++i) {
       Fixed value = AddSaturated<Fixed, min_value, max_value>(dst[i] - bias,
                                                               src[i] - bias);
       dst[i] = static_cast<Format>(value + bias);
     }
   } else {
     // General case -- have to adjust volume before mixing.
     const int fixed_volume = static_cast<int>(volume * 65536);
@@ skipping 219 matching lines @@
 
 bool IsWASAPISupported() {
   // Note: that function correctly returns that Windows Server 2003 does not
   // support WASAPI.
   return base::win::GetVersion() >= base::win::VERSION_VISTA;
 }
 
 #endif
 
 }  // namespace media