Use nullptr instead of 0 in WebAudio

Source/modules/webaudio/OfflineAudioContext.cpp

Index: Source/modules/webaudio/OfflineAudioContext.cpp
diff --git a/Source/modules/webaudio/OfflineAudioContext.cpp b/Source/modules/webaudio/OfflineAudioContext.cpp
index e70027f4dbe3e063f2c1a12bd3a9d239ba327a7a..19572eef044d23aaf08d396705aac030ad12f4d2 100644
--- a/Source/modules/webaudio/OfflineAudioContext.cpp
+++ b/Source/modules/webaudio/OfflineAudioContext.cpp
@@ -44,14 +44,14 @@ OfflineAudioContext* OfflineAudioContext::create(ExecutionContext* context, unsi
         exceptionState.throwDOMException(
             NotSupportedError,
             "Workers are not supported.");
-        return 0;
+        return nullptr;
     }
 
     Document* document = toDocument(context);
 
     if (!numberOfFrames) {
         exceptionState.throwDOMException(SyntaxError, "number of frames cannot be zero.");
-        return 0;
+        return nullptr;
     }
 
     if (numberOfChannels > AudioContext::maxNumberOfChannels()) {
@@ -64,7 +64,7 @@ OfflineAudioContext* OfflineAudioContext::create(ExecutionContext* context, unsi
                 ExceptionMessages::InclusiveBound,
                 AudioContext::maxNumberOfChannels(),
                 ExceptionMessages::InclusiveBound));
-        return 0;
+        return nullptr;
     }
 
     if (!AudioUtilities::isValidAudioBufferSampleRate(sampleRate)) {