Test resampling of AudioBuffers that have a different sample rate from the context

This is a follow up that adds a simple layout test to test
https://codereview.chromium.org/201673004/

This test creates an audio context at 48 kHz and a 3 kHz sine wave in
an AudioBuffer that is played through the context. The test verifies
that the output is sufficiently close to the expected sine wave output.

BUG=344375

Review URL: https://codereview.chromium.org/213153003

git-svn-id: svn://svn.chromium.org/blink/trunk@170197 bbb929c8-8fbe-4397-9dbb-9b2b20218538