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

media/base/audio_bus.h

Index: media/base/audio_bus.h
===================================================================
--- media/base/audio_bus.h	(revision 155897)
+++ media/base/audio_bus.h	(working copy)
@@ -45,6 +45,11 @@
   // Returns the required memory size to use the WrapMemory() method.
   static int CalculateMemorySize(const AudioParameters& params);
 
+  // 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 CalculateMemorySizeFromChannels(int channels, int frames,
+                                             int* aligned_frames);

[DaleCurtis, 2012/09/11 09:44:39]

I'd prefer this to be just CalculateMemorySize(int,int) and paired with the
method above both to keep style with the existing Create(int, int),
WrapMemory(int, int) methods and because FromChannels is only half the equation.
The (int, int) method be ordered first.

Per the style guide, overloading is fine "only if a reader looking at a call
site can get a good idea of what is happening without having to first figure out
exactly which overload is being called." Which fits the bill here. 

The aligned_frames value also shouldn't be exposed as we're leaking internal
details about the AudioBus. I don't see where you're using this value so lets
not expose it.

[scherkus (not reviewing), 2012/09/11 12:13:00]

Perhaps we need an internal impl w/ |aligned_frames| to remain inside the .cc as
a static method and expose a version here that doesn't return |aligned_frames|

[DaleCurtis, 2012/09/11 12:22:23]

Yes, that's what I was thinking. 

+
   // Helper methods for converting an AudioBus from and to interleaved integer
   // data.  Expects interleaving to be [ch0, ch1, ..., chN, ch0, ch1, ...] with
   // |bytes_per_sample| per value.  Values are scaled and bias corrected during