--- a/dom/media/eme/EMEUtils.cpp
+++ b/dom/media/eme/EMEUtils.cpp
@@ -1,15 +1,17 @@
 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this file,
  * You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 #include "mozilla/EMEUtils.h"
+
+#include "jsfriendapi.h"
 #include "mozilla/dom/UnionTypes.h"
 
 namespace mozilla {
 
 LogModule* GetEMELog() {
   static LazyLogModule log("EME");
   return log;
 }
@@ -18,40 +20,50 @@ LogModule* GetEMEVerboseLog() {
   static LazyLogModule log("EMEV");
   return log;
 }
 
 ArrayData GetArrayBufferViewOrArrayBufferData(
     const dom::ArrayBufferViewOrArrayBuffer& aBufferOrView) {
   MOZ_ASSERT(aBufferOrView.IsArrayBuffer() ||
              aBufferOrView.IsArrayBufferView());
+  JS::AutoCheckCannotGC nogc;
   if (aBufferOrView.IsArrayBuffer()) {
     const dom::ArrayBuffer& buffer = aBufferOrView.GetAsArrayBuffer();
     buffer.ComputeState();
     return ArrayData(buffer.Data(), buffer.Length());
   } else if (aBufferOrView.IsArrayBufferView()) {
     const dom::ArrayBufferView& bufferview =
         aBufferOrView.GetAsArrayBufferView();
     bufferview.ComputeState();
     return ArrayData(bufferview.Data(), bufferview.Length());
   }
   return ArrayData(nullptr, 0);
 }
 
 void CopyArrayBufferViewOrArrayBufferData(
     const dom::ArrayBufferViewOrArrayBuffer& aBufferOrView,
     nsTArray<uint8_t>& aOutData) {
+  JS::AutoCheckCannotGC nogc;
   ArrayData data = GetArrayBufferViewOrArrayBufferData(aBufferOrView);
   aOutData.Clear();
   if (!data.IsValid()) {
     return;
   }
   aOutData.AppendElements(data.mData, data.mLength);
 }
 
+void CopyArrayBufferViewOrArrayBufferData(const dom::ArrayBuffer& aBuffer,
+                                          nsTArray<uint8_t>& aOutData) {
+  JS::AutoCheckCannotGC nogc;
+  aBuffer.ComputeState();
+  aOutData.Clear();
+  aOutData.AppendElements(aBuffer.Data(), aBuffer.Length());
+}
+
 bool IsClearkeyKeySystem(const nsAString& aKeySystem) {
   return aKeySystem.EqualsLiteral(EME_KEY_SYSTEM_CLEARKEY);
 }
 
 bool IsWidevineKeySystem(const nsAString& aKeySystem) {
   return aKeySystem.EqualsLiteral(EME_KEY_SYSTEM_WIDEVINE);
 }
 

--- a/dom/media/eme/EMEUtils.h
+++ b/dom/media/eme/EMEUtils.h
@@ -42,16 +42,20 @@ LogModule* GetEMEVerboseLog();
 // Helper function to extract a copy of data coming in from JS in an
 // (ArrayBuffer or ArrayBufferView) IDL typed function argument.
 //
 // Only call this on a properly initialized ArrayBufferViewOrArrayBuffer.
 void CopyArrayBufferViewOrArrayBufferData(
     const dom::ArrayBufferViewOrArrayBuffer& aBufferOrView,
     nsTArray<uint8_t>& aOutData);
 
+// Overload for ArrayBuffer
+void CopyArrayBufferViewOrArrayBufferData(const dom::ArrayBuffer& aBufferOrView,
+                                          nsTArray<uint8_t>& aOutData);
+
 struct ArrayData {
   explicit ArrayData(const uint8_t* aData, size_t aLength)
       : mData(aData), mLength(aLength) {}
   const uint8_t* mData;
   const size_t mLength;
   bool IsValid() const { return mData != nullptr && mLength != 0; }
   bool operator==(const nsTArray<uint8_t>& aOther) const {
     return mLength == aOther.Length() &&

--- a/dom/media/eme/MediaEncryptedEvent.cpp
+++ b/dom/media/eme/MediaEncryptedEvent.cpp
@@ -73,18 +73,20 @@ already_AddRefed<MediaEncryptedEvent> Me
     const MediaKeyNeededEventInit& aEventInitDict, ErrorResult& aRv) {
   nsCOMPtr<EventTarget> owner = do_QueryInterface(aGlobal.GetAsSupports());
   RefPtr<MediaEncryptedEvent> e = new MediaEncryptedEvent(owner);
   bool trusted = e->Init(owner);
   e->InitEvent(aType, aEventInitDict.mBubbles, aEventInitDict.mCancelable);
   e->mInitDataType = aEventInitDict.mInitDataType;
   if (!aEventInitDict.mInitData.IsNull()) {
     const auto& a = aEventInitDict.mInitData.Value();
-    a.ComputeState();
-    e->mInitData = ArrayBuffer::Create(aGlobal.Context(), a.Length(), a.Data());
+    nsTArray<uint8_t> initData;
+    CopyArrayBufferViewOrArrayBufferData(a, initData);
+    e->mInitData = ArrayBuffer::Create(aGlobal.Context(), initData.Length(),
+                                       initData.Elements());
     if (!e->mInitData) {
       aRv.Throw(NS_ERROR_OUT_OF_MEMORY);
       return nullptr;
     }
   }
   e->SetTrusted(trusted);
   return e.forget();
 }

--- a/dom/media/eme/MediaKeyMessageEvent.cpp
+++ b/dom/media/eme/MediaKeyMessageEvent.cpp
@@ -71,20 +71,20 @@ already_AddRefed<MediaKeyMessageEvent> M
 
 already_AddRefed<MediaKeyMessageEvent> MediaKeyMessageEvent::Constructor(
     const GlobalObject& aGlobal, const nsAString& aType,
     const MediaKeyMessageEventInit& aEventInitDict, ErrorResult& aRv) {
   nsCOMPtr<EventTarget> owner = do_QueryInterface(aGlobal.GetAsSupports());
   RefPtr<MediaKeyMessageEvent> e = new MediaKeyMessageEvent(owner);
   bool trusted = e->Init(owner);
   e->InitEvent(aType, aEventInitDict.mBubbles, aEventInitDict.mCancelable);
-  aEventInitDict.mMessage.ComputeState();
-  e->mMessage =
-      ArrayBuffer::Create(aGlobal.Context(), aEventInitDict.mMessage.Length(),
-                          aEventInitDict.mMessage.Data());
+  nsTArray<uint8_t> initData;
+  CopyArrayBufferViewOrArrayBufferData(aEventInitDict.mMessage, initData);
+  e->mMessage = ArrayBuffer::Create(aGlobal.Context(), initData.Length(),
+                                    initData.Elements());
   if (!e->mMessage) {
     aRv.Throw(NS_ERROR_OUT_OF_MEMORY);
     return nullptr;
   }
   e->mMessageType = aEventInitDict.mMessageType;
   e->SetTrusted(trusted);
   e->SetComposed(aEventInitDict.mComposed);
   return e.forget();