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This is a partial port of WebAudio's SincResampler from WebKit formatted and
culled for use by Chrome Media.

We can't directly use the one in WebKit as it's layed under a ton of abstraction
and is tightly coupled with WebKit objects.

Test generates a swept sine wave and calculates the RMS error for common sample
rates (via UMA stats).

MultiChannelResampler and AudioRenderMixer changes to support resampling will
come in later CLs.

The 1000 ft view is that MultiChannelResampler will implement SincResampler::
AudioSourceProvider and AudioRendererMixer will implement a new
MultiChannelResampler::MultiChannelAudioSourceProvider interface.

When resampling is necessary AudioRenderMixer will feed itself into a
MultiChannelResampler instance which will poll data as necessary and feed it
channel by channel into a set of SincResamplers (one for each channel).

We want to resample post-mixing since resampling is a much more expensive
operation.

Original for reference:
http://git.chromium.org/gitweb/?p=external/Webkit.git&a=blob&f=Source/WebCore/platform/audio/SincResampler.cpp

Visual plot of 44100 to 48000 for reference; red line is the resampled signal
and the green line is the reference signal. Ideally only the pure signal (green)
should be seen.  Any bit of the resampled signal showing (red) is where the
resampling algorithm is incorrect: http://i.imgur.com/1vsaI.png

BUG=133637
TEST=New unittests.

Review URL: https://chromiumcodereview.appspot.com/10702050

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@146219 0039d316-1c4b-4281-b951-d872f2087c98