--- a/dom/base/nsDeprecatedOperationList.h
+++ b/dom/base/nsDeprecatedOperationList.h
@@ -45,8 +45,9 @@ DEPRECATED_OPERATION(NavigatorGetUserMed
 DEPRECATED_OPERATION(WebrtcDeprecatedPrefix)
 DEPRECATED_OPERATION(RTCPeerConnectionGetStreams)
 DEPRECATED_OPERATION(AppCache)
 DEPRECATED_OPERATION(PrefixedImageSmoothingEnabled)
 DEPRECATED_OPERATION(PrefixedFullscreenAPI)
 DEPRECATED_OPERATION(LenientSetter)
 DEPRECATED_OPERATION(FileLastModifiedDate)
 DEPRECATED_OPERATION(ImageBitmapRenderingContext_TransferImageBitmap)
+DEPRECATED_OPERATION(URLCreateObjectURL_MediaStream)

--- a/dom/bindings/BindingUtils.cpp
+++ b/dom/bindings/BindingUtils.cpp
@@ -3613,26 +3613,33 @@ DeprecationWarning(JSContext* aCx, JSObj
                    nsIDocument::DeprecatedOperations aOperation)
 {
   GlobalObject global(aCx, aObject);
   if (global.Failed()) {
     NS_ERROR("Could not create global for DeprecationWarning");
     return;
   }
 
+  DeprecationWarning(global, aOperation);
+}
+
+void
+DeprecationWarning(const GlobalObject& aGlobal,
+                   nsIDocument::DeprecatedOperations aOperation)
+{
   if (NS_IsMainThread()) {
-    nsCOMPtr<nsPIDOMWindowInner> window = do_QueryInterface(global.GetAsSupports());
+    nsCOMPtr<nsPIDOMWindowInner> window = do_QueryInterface(aGlobal.GetAsSupports());
     if (window && window->GetExtantDoc()) {
       window->GetExtantDoc()->WarnOnceAbout(aOperation);
     }
 
     return;
   }
 
-  WorkerPrivate* workerPrivate = GetWorkerPrivateFromContext(aCx);
+  WorkerPrivate* workerPrivate = GetWorkerPrivateFromContext(aGlobal.Context());
   if (!workerPrivate) {
     return;
   }
 
   RefPtr<DeprecationWarningRunnable> runnable =
     new DeprecationWarningRunnable(workerPrivate, aOperation);
   runnable->Dispatch();
 }

--- a/dom/bindings/BindingUtils.h
+++ b/dom/bindings/BindingUtils.h
@@ -3190,16 +3190,20 @@ void
 SetDocumentAndPageUseCounter(JSContext* aCx, JSObject* aObject,
                              UseCounter aUseCounter);
 
 // Warnings
 void
 DeprecationWarning(JSContext* aCx, JSObject* aObject,
                    nsIDocument::DeprecatedOperations aOperation);
 
+void
+DeprecationWarning(const GlobalObject& aGlobal,
+                   nsIDocument::DeprecatedOperations aOperation);
+
 // A callback to perform funToString on an interface object
 JSString*
 InterfaceObjectToString(JSContext* aCx, JS::Handle<JSObject*> aObject,
                         unsigned /* indent */);
 
 namespace binding_detail {
 // Get a JS global object that can be used for some temporary allocations.  The
 // idea is that this should be used for situations when you need to operate in

--- a/dom/locales/en-US/chrome/dom/dom.properties
+++ b/dom/locales/en-US/chrome/dom/dom.properties
@@ -316,8 +316,10 @@ LargeAllocationSuccess=This page was loa
 LargeAllocationNonGetRequest=A Large-Allocation header was ignored due to the load being triggered by a non-GET request.
 # LOCALIZATION NOTE: Do not translate "Large-Allocation", as it is a literal header name. Do not translate `window.opener`.
 LargeAllocationNotOnlyToplevelInTabGroup=A Large-Allocation header was ignored due to the presence of windows which have a reference to this browsing context through the frame hierarchy or window.opener.
 # LOCALIZATION NOTE: Do not translate "Large-Allocation", as it is a literal header name
 LargeAllocationNonE10S=A Large-Allocation header was ignored due to the document not being loaded out of process.
 GeolocationInsecureRequestIsForbidden=A Geolocation request can only be fulfilled in a secure context.
 # LOCALIZATION NOTE: Do not translate "Large-Allocation", as it is a literal header name.
 LargeAllocationNonWin32=This page would be loaded in a new process due to a Large-Allocation header, however Large-Allocation process creation is disabled on non-Win32 platforms.
+# LOCALIZATION NOTE: Do not translate URL.createObjectURL(MediaStream).
+URLCreateObjectURL_MediaStream=URL.createObjectURL(MediaStream) is deprecated and will be removed soon.

--- a/dom/url/URL.cpp
+++ b/dom/url/URL.cpp
@@ -1722,16 +1722,19 @@ URL::CreateObjectURL(const GlobalObject&
   }
 }
 
 void
 URL::CreateObjectURL(const GlobalObject& aGlobal, DOMMediaStream& aStream,
                      nsAString& aResult, ErrorResult& aRv)
 {
   MOZ_ASSERT(NS_IsMainThread());
+
+  DeprecationWarning(aGlobal, nsIDocument::eURLCreateObjectURL_MediaStream);
+
   URLMainThread::CreateObjectURL(aGlobal, aStream, aResult, aRv);
 }
 
 void
 URL::CreateObjectURL(const GlobalObject& aGlobal, MediaSource& aSource,
                      nsAString& aResult, ErrorResult& aRv)
 {
   MOZ_ASSERT(NS_IsMainThread());