Implement suspend() and resume() for OfflineAudioContext

LayoutTests/webaudio/offlineaudiocontext-suspend-resume-promise-expected.txt

Index: LayoutTests/webaudio/offlineaudiocontext-suspend-resume-promise-expected.txt
diff --git a/LayoutTests/webaudio/offlineaudiocontext-suspend-resume-promise-expected.txt b/LayoutTests/webaudio/offlineaudiocontext-suspend-resume-promise-expected.txt
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+Test promise resolution of OfflineAudioContext.resume() and OfflineAudioContext.suspend().
+
+On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE".
+
+
+PASS context.currentTime is equal to 0.
+PASS context.currentTime is equal to 0.25.
+PASS context.currentTime is equal to 0.5.
+PASS context.currentTime is equal to 0.75.
+PASS context.currentTime is equal to 1.
+PASS context.currentTime is equal to 1.25.
+PASS context.currentTime is equal to 1.5.
+PASS context.currentTime is equal to 1.75.
+PASS context.suspend(scheduledSuspendTime) rejected correctly (with InvalidStateError: cannot schedule a suspend at frame 25600 (2 seconds) because it is greater than or equal to the total render duration of 25600 frames).
+PASS context.state is equal to closed.
+PASS successfullyParsed is true
+
+TEST COMPLETE
+