Make media_blink_unittests compile on windows
This was the error before:
e:\b\build\slave\win\build\src\media\blink\webaudiosourceprovider_impl_unittest.cc(165) : error C2220: warning treated as error - no 'object' file generated
e:\b\build\slave\win\build\src\media\blink\webaudiosourceprovider_impl_unittest.cc(165) : warning C4267: 'argument' : conversion from 'size_t' to 'int', possible loss of data
BUG=506122
Review URL: https://codereview.chromium.org/
1346373004
Cr-Commit-Position: refs/heads/master@{#349266}