Support for AudioContextOptions latencyHint.

third_party/WebKit/Source/modules/webaudio/AudioContext.idl

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+enum AudioContextLatencyCategory {
+    "balanced",
+    "interactive",
+    "playback"
+};
+
 // See https://webaudio.github.io/web-audio-api/#AudioContext
 [
     ActiveScriptWrappable,
-    Constructor,
+    Constructor(optional AudioContextOptions contextOptions),
     ConstructorCallWith=Document,
     DependentLifetime,
     RaisesException=Constructor,
     Measure
 ] interface AudioContext : BaseAudioContext {
     [MeasureAs=AudioContextSuspend, CallWith=ScriptState, ImplementedAs=suspendContext] Promise<void> suspend();
     [MeasureAs=AudioContextClose, CallWith=ScriptState, ImplementedAs=closeContext] Promise<void> close();
 
     // Output timestamp
     [MeasureAs=AudioContextGetOutputTimestamp, CallWith=ScriptState] AudioTimestamp getOutputTimestamp();
 
+    // Number of seconds of processing latency incurred by the AudioContext
+    // passing the audio from the AudioDestinationNode to the audio subsystem
+    readonly attribute double baseLatency;
+
     // Sources
     // TODO(rtoy): The following methods should be here instead of in BaseAudioContext:
     //
     // createMediaElementSource(HTMLMediaElement mediaElement)
     // createMediaStreamSource(MediaStream mediaStream)
     // createMediaStreamDestination()
 };