Rebase oscillator sine test result.

Manually compared this new result against the linux result and they
differ by about 2 units, which is expected. The old result appears
to have a completely incorrect frequency sweep.

Also added a new test for oscillator that uses SNR and max difference to compare the expected and actual result. This is a bit more robust with different numerical results and makes it easier to tell if something is totally wrong or just slightly wrong for the oscillator-sine test.

Removed oscillator-sine; it seems very sensitive to numerics of the platform, and I think the new osc-sine-sweep-snr test is robust enough to catch errors

The other oscillator tests are just updated to match the change in api in oscillator-testing.js to support passing in the context so different check routines can be used for the test.

BUG=425744, 431688, 309197
TESTS=osc-sine-sweep-snr.html

Review URL: https://codereview.chromium.org/670863002

git-svn-id: svn://svn.chromium.org/blink/trunk@185249 bbb929c8-8fbe-4397-9dbb-9b2b20218538