diff --git a/dom/webidl/BluetoothAdapter2.webidl b/dom/webidl/BluetoothAdapter2.webidl
index 45d9d73b1967..829b64911dce 100644
--- a/dom/webidl/BluetoothAdapter2.webidl
+++ b/dom/webidl/BluetoothAdapter2.webidl
@@ -72,24 +72,24 @@ interface BluetoothAdapter : EventTarget {
    * Several onattributechanged events would be triggered during processing the
    * request, and the last one indicates adapter.state becomes enabled/disabled.
    */
-  [NewObject, Throws]
+  [NewObject]
   Promise<void> enable();
-  [NewObject, Throws]
+  [NewObject]
   Promise<void> disable();
 
-  [NewObject, Throws]
+  [NewObject]
   Promise<void> setName(DOMString aName);
-  [NewObject, Throws]
+  [NewObject]
   Promise<void> setDiscoverable(boolean aDiscoverable);
 
-  [NewObject, Throws]
+  [NewObject]
   Promise<BluetoothDiscoveryHandle> startDiscovery();
-  [NewObject, Throws]
+  [NewObject]
   Promise<void> stopDiscovery();
 
-  [NewObject, Throws]
+  [NewObject]
   Promise<void> pair(DOMString deviceAddress);
-  [NewObject, Throws]
+  [NewObject]
   Promise<void> unpair(DOMString deviceAddress);
 
   sequence<BluetoothDevice> getPairedDevices();
diff --git a/dom/webidl/BluetoothDevice2.webidl b/dom/webidl/BluetoothDevice2.webidl
index 2eceaca9e6c3..d1963bf061c4 100644
--- a/dom/webidl/BluetoothDevice2.webidl
+++ b/dom/webidl/BluetoothDevice2.webidl
@@ -26,7 +26,7 @@ interface BluetoothDevice : EventTarget
    * If the operation succeeds, the promise will be resolved with up-to-date
    * UUID list which is identical to attribute uuids.
    */
-  [NewObject, Throws]
+  [NewObject]
   Promise<sequence<DOMString>>              fetchUuids();
 };
 
diff --git a/dom/webidl/BluetoothPairingHandle.webidl b/dom/webidl/BluetoothPairingHandle.webidl
index 8a850b911b16..ad75fdcddc93 100644
--- a/dom/webidl/BluetoothPairingHandle.webidl
+++ b/dom/webidl/BluetoothPairingHandle.webidl
@@ -13,8 +13,8 @@ interface BluetoothPairingHandle
    */
   readonly attribute DOMString passkey;
 
-  [NewObject, Throws]
+  [NewObject]
   Promise<void> setPinCode(DOMString aPinCode);
-  [NewObject, Throws]
+  [NewObject]
   Promise<void> setPairingConfirmation(boolean aConfirm);
 };
diff --git a/dom/webidl/DOMRequest.webidl b/dom/webidl/DOMRequest.webidl
index 039446904563..53686ab11304 100644
--- a/dom/webidl/DOMRequest.webidl
+++ b/dom/webidl/DOMRequest.webidl
@@ -19,7 +19,7 @@ interface DOMRequestShared {
 interface DOMRequest : EventTarget {
   // The [TreatNonCallableAsNull] annotation is required since then() should do
   // nothing instead of throwing errors when non-callable arguments are passed.
-  [NewObject, Throws]
+  [NewObject]
   Promise<any> then([TreatNonCallableAsNull] optional AnyCallback? fulfillCallback = null,
                     [TreatNonCallableAsNull] optional AnyCallback? rejectCallback = null);
 };
diff --git a/dom/webidl/DeviceStorage.webidl b/dom/webidl/DeviceStorage.webidl
index ba2d6a4a1b2a..2b31fcc3fcf1 100644
--- a/dom/webidl/DeviceStorage.webidl
+++ b/dom/webidl/DeviceStorage.webidl
@@ -86,7 +86,7 @@ interface DeviceStorage : EventTarget {
   // Indicates if the storage area denoted by storageName is removable
   readonly attribute boolean isRemovable;
 
-  [NewObject, Throws]
+  [NewObject]
   // XXXbz what type does this really return?
   Promise<any> getRoot();
 };
diff --git a/dom/webidl/Directory.webidl b/dom/webidl/Directory.webidl
index cab6b4210edd..f60b2ad6bb9d 100644
--- a/dom/webidl/Directory.webidl
+++ b/dom/webidl/Directory.webidl
@@ -35,7 +35,7 @@ interface Directory {
    * @return If succeeds, the promise is resolved with the new created
    * File object. Otherwise, rejected with a DOM error.
    */
-  [NewObject, Throws]
+  [NewObject]
   Promise<File> createFile(DOMString path, optional CreateFileOptions options);
 
   /*
@@ -47,7 +47,7 @@ interface Directory {
    * @return If succeeds, the promise is resolved with the new created
    * Directory object. Otherwise, rejected with a DOM error.
    */
-  [NewObject, Throws]
+  [NewObject]
   Promise<Directory> createDirectory(DOMString path);
 
   /*
@@ -58,7 +58,7 @@ interface Directory {
    * with a File or Directory object, depending on the entry's type. Otherwise,
    * rejected with a DOM error.
    */
-  [NewObject, Throws]
+  [NewObject]
   Promise<(File or Directory)> get(DOMString path);
 
   /*
@@ -72,7 +72,7 @@ interface Directory {
    * exist, the promise is resolved with boolean false. If the target did exist
    * and was successfully deleted, the promise is resolved with boolean true.
    */
-  [NewObject, Throws]
+  [NewObject]
   Promise<boolean> remove((DOMString or File or Directory) path);
 
   /*
@@ -86,7 +86,7 @@ interface Directory {
    * resolved with boolean false. If the target did exist and was successfully
    * deleted, the promise is resolved with boolean true.
    */
-  [NewObject, Throws]
+  [NewObject]
   Promise<boolean> removeDeep((DOMString or File or Directory) path);
 };
 
diff --git a/dom/webidl/HTMLMediaElement.webidl b/dom/webidl/HTMLMediaElement.webidl
index 48426bdd8873..8522738c487d 100644
--- a/dom/webidl/HTMLMediaElement.webidl
+++ b/dom/webidl/HTMLMediaElement.webidl
@@ -151,7 +151,7 @@ partial interface HTMLMediaElement {
   readonly attribute MediaKeys? mediaKeys;
 
   // void, not any: https://www.w3.org/Bugs/Public/show_bug.cgi?id=26457
-  [Pref="media.eme.enabled", Throws, NewObject]
+  [Pref="media.eme.enabled", NewObject]
   Promise<void> setMediaKeys(MediaKeys? mediaKeys);
 
   [Pref="media.eme.enabled"]
diff --git a/dom/webidl/MediaKeySession.webidl b/dom/webidl/MediaKeySession.webidl
index 4a1274ad50d7..dade9b02b795 100644
--- a/dom/webidl/MediaKeySession.webidl
+++ b/dom/webidl/MediaKeySession.webidl
@@ -23,22 +23,22 @@ interface MediaKeySession : EventTarget {
 
   readonly attribute Promise<void> closed;
 
-  [NewObject, Throws]
+  [NewObject]
   Promise<void> generateRequest(DOMString initDataType, (ArrayBufferView or ArrayBuffer) initData);
 
-  [NewObject, Throws]
+  [NewObject]
   Promise<boolean> load(DOMString sessionId);
 
   // session operations
-  [NewObject, Throws]
+  [NewObject]
   Promise<void> update((ArrayBufferView or ArrayBuffer) response);
 
-  [NewObject, Throws]
+  [NewObject]
   Promise<void> close();
 
-  [NewObject, Throws]
+  [NewObject]
   Promise<void> remove();
 
-  [NewObject, Throws]
+  [NewObject]
   Promise<sequence<ArrayBuffer>> getUsableKeyIds();
 };
diff --git a/dom/webidl/MediaKeySystemAccess.webidl b/dom/webidl/MediaKeySystemAccess.webidl
index 9c62a8443c1e..817b29c694e6 100644
--- a/dom/webidl/MediaKeySystemAccess.webidl
+++ b/dom/webidl/MediaKeySystemAccess.webidl
@@ -29,6 +29,6 @@ dictionary MediaKeySystemOptions {
 [Pref="media.eme.enabled"]
 interface MediaKeySystemAccess {
   readonly    attribute DOMString keySystem;
-  [NewObject, Throws]
+  [NewObject]
   Promise<MediaKeys> createMediaKeys();
 };
diff --git a/dom/webidl/MediaKeys.webidl b/dom/webidl/MediaKeys.webidl
index c0bf381c5ccd..3a8dd6192562 100644
--- a/dom/webidl/MediaKeys.webidl
+++ b/dom/webidl/MediaKeys.webidl
@@ -20,6 +20,6 @@ interface MediaKeys {
   [NewObject, Throws]
   MediaKeySession createSession(optional SessionType sessionType = "temporary");
 
-  [NewObject, Throws]
+  [NewObject]
   Promise<void> setServerCertificate((ArrayBufferView or ArrayBuffer) serverCertificate);
 };
diff --git a/dom/webidl/MozIcc.webidl b/dom/webidl/MozIcc.webidl
index 09c71b84c897..693872c43fb7 100644
--- a/dom/webidl/MozIcc.webidl
+++ b/dom/webidl/MozIcc.webidl
@@ -351,6 +351,6 @@ interface MozIcc : EventTarget
    *         If succeeds, the promise is resolved with boolean indicating the
    *         availability of the service. Otherwise, rejected with a DOMError.
    */
-  [NewObject, Throws]
+  [NewObject]
   Promise<boolean> getServiceState(IccService service);
 };
diff --git a/dom/webidl/Navigator.webidl b/dom/webidl/Navigator.webidl
index 720b082e14d0..78ac2197d003 100644
--- a/dom/webidl/Navigator.webidl
+++ b/dom/webidl/Navigator.webidl
@@ -132,7 +132,7 @@ Navigator implements NavigatorBattery;
 [NoInterfaceObject,
  Exposed=(Window,Worker)]
 interface NavigatorDataStore {
-    [Throws, NewObject, Func="Navigator::HasDataStoreSupport"]
+    [NewObject, Func="Navigator::HasDataStoreSupport"]
     Promise<sequence<DataStore>> getDataStores(DOMString name,
                                                optional DOMString? owner = null);
 };
@@ -173,7 +173,7 @@ interface NavigatorMobileId {
     // permission is set to PROMPT_ACTION and [CheckPermissions] only checks
     // for ALLOW_ACTION.
     // XXXbz what is this promise resolved with?
-    [Throws, NewObject, Func="Navigator::HasMobileIdSupport"]
+    [NewObject, Func="Navigator::HasMobileIdSupport"]
     Promise<any> getMobileIdAssertion(optional MobileIdOptions options);
 };
 Navigator implements NavigatorMobileId;
@@ -405,7 +405,7 @@ partial interface Navigator {
 
 #ifdef MOZ_EME
 partial interface Navigator {
-  [Pref="media.eme.enabled", Throws, NewObject]
+  [Pref="media.eme.enabled", NewObject]
   Promise<MediaKeySystemAccess>
   requestMediaKeySystemAccess(DOMString keySystem,
                               optional sequence<MediaKeySystemOptions> supportedConfigurations);
diff --git a/dom/webidl/Promise.webidl b/dom/webidl/Promise.webidl
index 1c19433b7bca..1f22f58e2084 100644
--- a/dom/webidl/Promise.webidl
+++ b/dom/webidl/Promise.webidl
@@ -27,23 +27,23 @@ interface _Promise {
   // the proto of a promise object or someone screws up and manages to create a
   // Promise object in this scope without having resolved the interface object
   // first.
-  [NewObject, Throws]
+  [NewObject]
   static Promise<any> resolve(optional any value);
-  [NewObject, Throws]
+  [NewObject]
   static Promise<void> reject(optional any value);
 
   // The [TreatNonCallableAsNull] annotation is required since then() should do
   // nothing instead of throwing errors when non-callable arguments are passed.
-  [NewObject, Throws]
+  [NewObject]
   Promise<any> then([TreatNonCallableAsNull] optional AnyCallback? fulfillCallback = null,
                     [TreatNonCallableAsNull] optional AnyCallback? rejectCallback = null);
 
-  [NewObject, Throws]
+  [NewObject]
   Promise<any> catch([TreatNonCallableAsNull] optional AnyCallback? rejectCallback = null);
 
-  [NewObject, Throws]
+  [NewObject]
   static Promise<any> all(sequence<any> iterable);
 
-  [NewObject, Throws]
+  [NewObject]
   static Promise<any> race(sequence<any> iterable);
 };
diff --git a/dom/webidl/TelephonyCall.webidl b/dom/webidl/TelephonyCall.webidl
index 1bfc2c2b901f..022e4a6bb418 100644
--- a/dom/webidl/TelephonyCall.webidl
+++ b/dom/webidl/TelephonyCall.webidl
@@ -33,13 +33,13 @@ interface TelephonyCall : EventTarget {
 
   readonly attribute TelephonyCallGroup? group;
 
-  [NewObject, Throws]
+  [NewObject]
   Promise<void> answer();
-  [NewObject, Throws]
+  [NewObject]
   Promise<void> hangUp();
-  [NewObject, Throws]
+  [NewObject]
   Promise<void> hold();
-  [NewObject, Throws]
+  [NewObject]
   Promise<void> resume();
 
   attribute EventHandler onstatechange;
diff --git a/dom/webidl/TelephonyCallGroup.webidl b/dom/webidl/TelephonyCallGroup.webidl
index f3539b5b2d81..a51ccd485223 100644
--- a/dom/webidl/TelephonyCallGroup.webidl
+++ b/dom/webidl/TelephonyCallGroup.webidl
@@ -17,7 +17,7 @@ interface TelephonyCallGroup : EventTarget {
   [Throws]
   void remove(TelephonyCall call);
 
-  [NewObject, Throws]
+  [NewObject]
   Promise<void> hangUp();
 
   [Throws]
diff --git a/dom/webidl/TextEncoder.webidl b/dom/webidl/TextEncoder.webidl
index 3b6973b86870..a031e6d26207 100644
--- a/dom/webidl/TextEncoder.webidl
+++ b/dom/webidl/TextEncoder.webidl
@@ -15,6 +15,6 @@
 interface TextEncoder {
   [Constant]
   readonly attribute DOMString encoding;
-  [Throws, NewObject]
+  [NewObject]
   Uint8Array encode(optional USVString input = "");
 };
diff --git a/dom/webidl/USSDSession.webidl b/dom/webidl/USSDSession.webidl
index 4a843de236f2..5909bb7112e7 100644
--- a/dom/webidl/USSDSession.webidl
+++ b/dom/webidl/USSDSession.webidl
@@ -9,9 +9,9 @@
  AvailableIn="CertifiedApps",
  Constructor(unsigned long serviceId)]
 interface USSDSession {
-  [NewObject, Throws]
+  [NewObject]
   Promise<void> send(DOMString ussd);
 
-  [NewObject, Throws]
+  [NewObject]
   Promise<void> cancel();
 };