Add WASAPI-based unified audio I/O back-end for Windows 7.

Add WASAPI-based unified audio I/O back-end for Windows 7.

Implementation of AudioOuputStream for Windows using the WASAPI API.
Both input and output device must use the same sample rate.

Corresponding implementation for Mac OS X is given by http://codereview.chromium.org/10916105/.

Additional test using full Chrome:
http://webaudiodemos.appspot.com/input/index.html

Local tests have been performed using a wide range of audio devices and sample rates. It has also been verified that the QoS is good between two different devices as well as long as they both run at the same sample rate.

12 hour test of http://webaudiodemos.appspot.com/input/index.html worked well.

Verified that we log a warning "Unified audio I/O is not supported." if the user has selected different sample rates for in and out.

BUG=145092
TEST=media_unittests.exe --gtest_filter=WASAPIUnified* --enable-webaudio-input

Review URL: https://codereview.chromium.org/10959068

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@160346 0039d316-1c4b-4281-b951-d872f2087c98