Allow audio system to handle synchronized low-latency audio I/O

media/base/audio_bus.cc

Index: media/base/audio_bus.cc
===================================================================
--- media/base/audio_bus.cc	(revision 155437)
+++ media/base/audio_bus.cc	(working copy)
@@ -17,19 +17,6 @@
           (AudioBus::kChannelAlignment - 1)) == 0U;
 }
 
-// Calculates the required size for an AudioBus with the given params, sets
-// |aligned_frames| to the actual frame length of each channel array.
-static int CalculateMemorySizeInternal(int channels, int frames,
-                                       int* aligned_frames) {
-  CHECK(aligned_frames);
-  // Choose a size such that each channel will be aligned by kChannelAlignment
-  // when stored in a contiguous block.
-  *aligned_frames =
-      ((frames * sizeof(float) + AudioBus::kChannelAlignment - 1) &
-       ~(AudioBus::kChannelAlignment - 1)) / sizeof(float);
-  return sizeof(float) * channels * (*aligned_frames);
-}
-
 // |Format| is the destination type, |Fixed| is a type larger than |Format|
 // such that operations can be made without overflowing.
 template<class Format, class Fixed>
@@ -106,7 +93,7 @@
   ValidateConfig(channels, frames_);
 
   int aligned_frames = 0;
-  int size = CalculateMemorySizeInternal(channels, frames, &aligned_frames);
+  int size = CalculateMemorySizeFromChannels(channels, frames, &aligned_frames);
 
   data_.reset(static_cast<float*>(base::AlignedAlloc(
       size, AudioBus::kChannelAlignment)));
@@ -119,7 +106,7 @@
   ValidateConfig(channels, frames_);
 
   int aligned_frames = 0;
-  CalculateMemorySizeInternal(channels, frames, &aligned_frames);
+  CalculateMemorySizeFromChannels(channels, frames, &aligned_frames);
 
   BuildChannelData(channels, aligned_frames, data);
 }
@@ -187,9 +174,25 @@
   ZeroFrames(frames_);
 }
 
+// Calculates the required size for an AudioBus with the given params, sets
+// |aligned_frames| to the actual frame length of each channel array.
+int AudioBus::CalculateMemorySizeFromChannels(int channels, int frames,
+                                              int* out_aligned_frames) {
+  // Choose a size such that each channel will be aligned by
+  // kChannelAlignment when stored in a contiguous block.
+  int aligned_frames =
+      ((frames * sizeof(float) + AudioBus::kChannelAlignment - 1) &
+       ~(AudioBus::kChannelAlignment - 1)) / sizeof(float);
+
+  if (out_aligned_frames)
+    *out_aligned_frames = aligned_frames;
+
+  return sizeof(float) * channels * aligned_frames;
+}
+
 int AudioBus::CalculateMemorySize(const AudioParameters& params) {
   int aligned_frames = 0;
-  return CalculateMemorySizeInternal(
+  return CalculateMemorySizeFromChannels(
       params.channels(), params.frames_per_buffer(), &aligned_frames);
 }