Replace oscillator tests with more robust tests

LayoutTests/TestExpectations

Index: LayoutTests/TestExpectations
diff --git a/LayoutTests/TestExpectations b/LayoutTests/TestExpectations
index 75fc914251b736661d822cffe5c52ef2a44a3a7d..201afcd87c1bf7084d1495da0a936e0fcbc92ec7 100644
--- a/LayoutTests/TestExpectations
+++ b/LayoutTests/TestExpectations
@@ -610,9 +610,6 @@ crbug.com/313846 http/tests/images/webp-partial-load.html [ ImageOnlyFailure Tim
 
 crbug.com/316730 canvas/synchronous-create-pattern.html [ ImageOnlyFailure Pass ]
 
-crbug.com/320099 webaudio/oscillator-sawtooth.html [ NeedsManualRebaseline ]
-crbug.com/320099 webaudio/oscillator-triangle.html [ NeedsManualRebaseline ]
-
 crbug.com/390125 media/video-frame-accurate-seek.html [ NeedsManualRebaseline ]
 
 crbug.com/245556 compositing/transitions/transform-on-large-layer.html [ ImageOnlyFailure ]
@@ -773,9 +770,6 @@ crbug.com/334269 [ Mac ] virtual/antialiasedtext/fast/text/whitespace/018.html [
 crbug.com/347365 [ Linux ] dom/xhtml/level3/core/canonicalform08.xhtml [ Crash Pass ]
 crbug.com/347365 [ Linux ] dom/xhtml/level3/core/canonicalform09.xhtml [ Crash Pass ]
 
-crbug.com/309197 [ Win Debug ] webaudio/oscillator-custom.html [ Skip ]
-crbug.com/309197 [ Win Debug ] webaudio/oscillator-square.html [ Skip ]
-
 crbug.com/356777 http/tests/history/frameset-repeated-name.html [ Pass Failure ]
 
 crbug.com/390377 [ Release ] fast/dom/private_script_unittest.html [ Skip ]