--- a/dom/media/eme/MediaKeySession.cpp
+++ b/dom/media/eme/MediaKeySession.cpp
@@ -50,23 +50,21 @@ static const uint32_t MAX_KEY_ID_LENGTH 
 // platform tests.
 static const uint32_t MAX_CENC_INIT_DATA_LENGTH = 64 * 1024;
 
 
 MediaKeySession::MediaKeySession(JSContext* aCx,
                                  nsPIDOMWindowInner* aParent,
                                  MediaKeys* aKeys,
                                  const nsAString& aKeySystem,
-                                 const nsAString& aCDMVersion,
                                  MediaKeySessionType aSessionType,
                                  ErrorResult& aRv)
   : DOMEventTargetHelper(aParent)
   , mKeys(aKeys)
   , mKeySystem(aKeySystem)
-  , mCDMVersion(aCDMVersion)
   , mSessionType(aSessionType)
   , mToken(sMediaKeySessionNum++)
   , mIsClosed(false)
   , mUninitialized(true)
   , mKeyStatusMap(new MediaKeyStatusMap(aParent))
   , mExpiration(JS::GenericNaN())
 {
   EME_LOG("MediaKeySession[%p,''] ctor", this);

--- a/dom/media/eme/MediaKeySession.h
+++ b/dom/media/eme/MediaKeySession.h
@@ -36,17 +36,16 @@ public:
   NS_DECL_ISUPPORTS_INHERITED
   NS_DECL_CYCLE_COLLECTION_CLASS_INHERITED(MediaKeySession,
                                            DOMEventTargetHelper)
 public:
   MediaKeySession(JSContext* aCx,
                   nsPIDOMWindowInner* aParent,
                   MediaKeys* aKeys,
                   const nsAString& aKeySystem,
-                  const nsAString& aCDMVersion,
                   MediaKeySessionType aSessionType,
                   ErrorResult& aRv);
 
   void SetSessionId(const nsAString& aSessionId);
 
   JSObject* WrapObject(JSContext* aCx, JS::Handle<JSObject*> aGivenProto) override;
 
   // Mark this as resultNotAddRefed to return raw pointers
@@ -118,17 +117,16 @@ private:
   already_AddRefed<DetailedPromise> MakePromise(ErrorResult& aRv,
                                                 const nsACString& aName);
 
   RefPtr<DetailedPromise> mClosed;
 
   RefPtr<MediaKeyError> mMediaKeyError;
   RefPtr<MediaKeys> mKeys;
   const nsString mKeySystem;
-  const nsString mCDMVersion;
   nsString mSessionId;
   const MediaKeySessionType mSessionType;
   const uint32_t mToken;
   bool mIsClosed;
   bool mUninitialized;
   RefPtr<MediaKeyStatusMap> mKeyStatusMap;
   double mExpiration;
 };

--- a/dom/media/eme/MediaKeySystemAccess.cpp
+++ b/dom/media/eme/MediaKeySystemAccess.cpp
@@ -48,21 +48,19 @@ NS_IMPL_CYCLE_COLLECTING_ADDREF(MediaKey
 NS_IMPL_CYCLE_COLLECTING_RELEASE(MediaKeySystemAccess)
 NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(MediaKeySystemAccess)
   NS_WRAPPERCACHE_INTERFACE_MAP_ENTRY
   NS_INTERFACE_MAP_ENTRY(nsISupports)
 NS_INTERFACE_MAP_END
 
 MediaKeySystemAccess::MediaKeySystemAccess(nsPIDOMWindowInner* aParent,
                                            const nsAString& aKeySystem,
-                                           const nsAString& aCDMVersion,
                                            const MediaKeySystemConfiguration& aConfig)
   : mParent(aParent)
   , mKeySystem(aKeySystem)
-  , mCDMVersion(aCDMVersion)
   , mConfig(aConfig)
 {
 }
 
 MediaKeySystemAccess::~MediaKeySystemAccess()
 {
 }
 
@@ -90,17 +88,16 @@ MediaKeySystemAccess::GetConfiguration(M
   aConfig = mConfig;
 }
 
 already_AddRefed<Promise>
 MediaKeySystemAccess::CreateMediaKeys(ErrorResult& aRv)
 {
   RefPtr<MediaKeys> keys(new MediaKeys(mParent,
                                        mKeySystem,
-                                       mCDMVersion,
                                        mConfig));
   return keys->Init(aRv);
 }
 
 static bool
 HaveGMPFor(mozIGeckoMediaPluginService* aGMPService,
            const nsCString& aKeySystem,
            const nsCString& aAPI,

--- a/dom/media/eme/MediaKeySystemAccess.h
+++ b/dom/media/eme/MediaKeySystemAccess.h
@@ -29,35 +29,32 @@ class MediaKeySystemAccess final : publi
 {
 public:
   NS_DECL_CYCLE_COLLECTING_ISUPPORTS
   NS_DECL_CYCLE_COLLECTION_SCRIPT_HOLDER_CLASS(MediaKeySystemAccess)
 
 public:
   explicit MediaKeySystemAccess(nsPIDOMWindowInner* aParent,
                                 const nsAString& aKeySystem,
-                                const nsAString& aCDMVersion,
                                 const MediaKeySystemConfiguration& aConfig);
 
 protected:
   ~MediaKeySystemAccess();
 
 public:
   nsPIDOMWindowInner* GetParentObject() const;
 
   JSObject* WrapObject(JSContext* aCx, JS::Handle<JSObject*> aGivenProto) override;
 
   void GetKeySystem(nsString& aRetVal) const;
 
   void GetConfiguration(MediaKeySystemConfiguration& aConfig);
 
   already_AddRefed<Promise> CreateMediaKeys(ErrorResult& aRv);
 
-
-
   static MediaKeySystemStatus GetKeySystemStatus(const nsAString& aKeySystem,
                                                  int32_t aMinCdmVersion,
                                                  nsACString& aOutExceptionMessage,
                                                  nsACString& aOutCdmVersion);
 
   static bool IsSupported(const nsAString& aKeySystem,
                           const Sequence<MediaKeySystemConfiguration>& aConfigs,
                           DecoderDoctorDiagnostics* aDiagnostics);
@@ -72,16 +69,15 @@ public:
                                  DecoderDoctorDiagnostics* aDiagnostics);
 
   static bool KeySystemSupportsInitDataType(const nsAString& aKeySystem,
                                             const nsAString& aInitDataType);
 
 private:
   nsCOMPtr<nsPIDOMWindowInner> mParent;
   const nsString mKeySystem;
-  const nsString mCDMVersion;
   const MediaKeySystemConfiguration mConfig;
 };
 
 } // namespace dom
 } // namespace mozilla
 
 #endif // mozilla_dom_MediaKeySystemAccess_h

--- a/dom/media/eme/MediaKeySystemAccessManager.cpp
+++ b/dom/media/eme/MediaKeySystemAccessManager.cpp
@@ -177,17 +177,17 @@ MediaKeySystemAccessManager::Request(Det
     diagnostics.StoreMediaKeySystemAccess(mWindow->GetExtantDoc(),
                                           aKeySystem, false, __func__);
     return;
   }
 
   MediaKeySystemConfiguration config;
   if (MediaKeySystemAccess::GetSupportedConfig(keySystem, aConfigs, config, &diagnostics)) {
     RefPtr<MediaKeySystemAccess> access(
-      new MediaKeySystemAccess(mWindow, keySystem, NS_ConvertUTF8toUTF16(cdmVersion), config));
+      new MediaKeySystemAccess(mWindow, aKeySystem, config));
     aPromise->MaybeResolve(access);
     diagnostics.StoreMediaKeySystemAccess(mWindow->GetExtantDoc(),
                                           aKeySystem, true, __func__);
     return;
   }
   // Not to inform user, because nothing to do if the corresponding keySystem
   // configuration is not supported.
   aPromise->MaybeReject(NS_ERROR_DOM_NOT_SUPPORTED_ERR,

--- a/dom/media/eme/MediaKeys.cpp
+++ b/dom/media/eme/MediaKeys.cpp
@@ -44,21 +44,19 @@ NS_IMPL_CYCLE_COLLECTING_ADDREF(MediaKey
 NS_IMPL_CYCLE_COLLECTING_RELEASE(MediaKeys)
 NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(MediaKeys)
   NS_WRAPPERCACHE_INTERFACE_MAP_ENTRY
   NS_INTERFACE_MAP_ENTRY(nsISupports)
 NS_INTERFACE_MAP_END
 
 MediaKeys::MediaKeys(nsPIDOMWindowInner* aParent,
                      const nsAString& aKeySystem,
-                     const nsAString& aCDMVersion,
                      const MediaKeySystemConfiguration& aConfig)
   : mParent(aParent)
   , mKeySystem(aKeySystem)
-  , mCDMVersion(aCDMVersion)
   , mCreatePromiseId(0)
   , mConfig(aConfig)
 {
   EME_LOG("MediaKeys[%p] constructed keySystem=%s",
           this, NS_ConvertUTF16toUTF8(mKeySystem).get());
 }
 
 MediaKeys::~MediaKeys()
@@ -478,22 +476,21 @@ MediaKeys::CreateSession(JSContext* aCx,
     NS_WARNING("Tried to use a MediaKeys which lost its CDM");
     aRv.Throw(NS_ERROR_DOM_INVALID_STATE_ERR);
     return nullptr;
   }
 
   EME_LOG("MediaKeys[%p] Creating session", this);
 
   RefPtr<MediaKeySession> session = new MediaKeySession(aCx,
-                                                          GetParentObject(),
-                                                          this,
-                                                          mKeySystem,
-                                                          mCDMVersion,
-                                                          aSessionType,
-                                                          aRv);
+                                                        GetParentObject(),
+                                                        this,
+                                                        mKeySystem,
+                                                        aSessionType,
+                                                        aRv);
 
   if (aRv.Failed()) {
     return nullptr;
   }
 
   // Add session to the set of sessions awaiting their sessionId being ready.
   mPendingSessions.Put(session->Token(), session);
 

--- a/dom/media/eme/MediaKeys.h
+++ b/dom/media/eme/MediaKeys.h
@@ -47,17 +47,16 @@ class MediaKeys final : public nsISuppor
 
 public:
   NS_DECL_CYCLE_COLLECTING_ISUPPORTS
   NS_DECL_CYCLE_COLLECTION_SCRIPT_HOLDER_CLASS(MediaKeys)
   MOZ_DECLARE_WEAKREFERENCE_TYPENAME(MediaKeys)
 
   MediaKeys(nsPIDOMWindowInner* aParentWindow,
             const nsAString& aKeySystem,
-            const nsAString& aCDMVersion,
             const MediaKeySystemConfiguration& aConfig);
 
   already_AddRefed<DetailedPromise> Init(ErrorResult& aRv);
 
   nsPIDOMWindowInner* GetParentObject() const;
 
   JSObject* WrapObject(JSContext* aCx, JS::Handle<JSObject*> aGivenProto) override;
 
@@ -142,17 +141,16 @@ private:
   // Owning ref to proxy. The proxy has a weak reference back to the MediaKeys,
   // and the MediaKeys destructor clears the proxy's reference to the MediaKeys.
   RefPtr<CDMProxy> mProxy;
 
   RefPtr<HTMLMediaElement> mElement;
 
   nsCOMPtr<nsPIDOMWindowInner> mParent;
   const nsString mKeySystem;
-  const nsString mCDMVersion;
   nsCString mNodeId;
   KeySessionHashMap mKeySessions;
   PromiseHashMap mPromises;
   PendingKeySessionsHashMap mPendingSessions;
   PromiseId mCreatePromiseId;
 
   RefPtr<nsIPrincipal> mPrincipal;
   RefPtr<nsIPrincipal> mTopLevelPrincipal;