Split "Online" and "Offline" AudioContext processing

Source/modules/modules.gypi

 {
   'includes': [
     '../core/core_generated.gypi',
     'modules_generated.gypi',
   ],
   'variables': {
     # Experimental hooks for embedder to provide extra IDL and source files.
     #
     # Note: this is not a supported API. If you rely on this, you will be broken
     # from time to time as the code generator changes in backward incompatible
@@ skipping 1347 matching lines @@
       'vr/VREyeParameters.h',
       'vr/VRFieldOfView.h',
       'vr/VRGetDevicesCallback.cpp',
       'vr/VRGetDevicesCallback.h',
       'vr/VRHardwareUnit.cpp',
       'vr/VRHardwareUnit.h',
       'vr/VRHardwareUnitCollection.cpp',
       'vr/VRHardwareUnitCollection.h',
       'vr/VRPositionState.cpp',
       'vr/VRPositionState.h',
+      'webaudio/AbstractAudioContext.cpp',
+      'webaudio/AbstractAudioContext.h',
       'webaudio/AnalyserNode.cpp',
       'webaudio/AnalyserNode.h',
       'webaudio/AsyncAudioDecoder.cpp',
       'webaudio/AsyncAudioDecoder.h',
       'webaudio/AudioBasicInspectorNode.cpp',
       'webaudio/AudioBasicInspectorNode.h',
       'webaudio/AudioBasicProcessorHandler.cpp',
       'webaudio/AudioBasicProcessorHandler.h',
       'webaudio/AudioBuffer.cpp',
       'webaudio/AudioBuffer.h',
@@ skipping 346 matching lines @@
       'webaudio/AudioBasicProcessorHandlerTest.cpp',
       'webaudio/ConvolverNodeTest.cpp',
       'webaudio/DynamicsCompressorNodeTest.cpp',
       'webaudio/ScriptProcessorNodeTest.cpp',
       'webaudio/StereoPannerNodeTest.cpp',
       'websockets/DOMWebSocketTest.cpp',
       'websockets/DocumentWebSocketChannelTest.cpp',
     ],
   },
 }