OfflineAudioContext should support up to 32 channels.

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 71dccde0905ad1c8f7c631c55ed21044afa3bb51..d780fac53ec1e6c00c90b8fdc41400cc1b328dbf 100644
--- a/Source/modules/webaudio/OfflineAudioContext.cpp
+++ b/Source/modules/webaudio/OfflineAudioContext.cpp
@@ -53,8 +53,16 @@ PassRefPtr<OfflineAudioContext> OfflineAudioContext::create(ExecutionContext* co
         return nullptr;
     }
 
-    if (numberOfChannels > 10) {
-        exceptionState.throwDOMException(SyntaxError, "number of channels (" + String::number(numberOfChannels) + ") exceeds maximum (10).");
+    if (numberOfChannels > AudioContext::maxNumberOfChannels()) {
+        exceptionState.throwDOMException(
+            IndexSizeError,
+            ExceptionMessages::indexOutsideRange<unsigned>(
+                "number of channels",
+                numberOfChannels,
+                0,
+                ExceptionMessages::InclusiveBound,
+                AudioContext::maxNumberOfChannels(),
+                ExceptionMessages::InclusiveBound));
         return nullptr;
     }