--- a/dom/chrome-webidl/BrowsingContext.webidl
+++ b/dom/chrome-webidl/BrowsingContext.webidl
@@ -1,16 +1,16 @@
 /* -*- Mode: IDL; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
 /* 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/. */
 
 interface nsIDocShell;
 
-[Exposed=(Window, System), ChromeOnly]
+[Exposed=Window, ChromeOnly]
 interface BrowsingContext {
   readonly attribute BrowsingContext? parent;
 
   sequence<BrowsingContext> getChildren();
 
   readonly attribute nsIDocShell? docShell;
 
   readonly attribute unsigned long long id;

--- a/dom/chrome-webidl/ChromeUtils.webidl
+++ b/dom/chrome-webidl/ChromeUtils.webidl
@@ -9,28 +9,28 @@
  *
  * For JS callers, this behaves like a normal QueryInterface function. When
  * called with a supported interface, it returns its `this` object. When
  * called with an unsupported interface, it throws NS_ERROR_NO_INTERFACE.
  *
  * C++ callers use a fast path, and never call the JSAPI or WebIDL methods of
  * this object.
  */
-[ChromeOnly, Exposed=(Window,System)]
+[ChromeOnly, Exposed=Window]
 interface MozQueryInterface {
   [Throws]
   legacycaller any (IID aIID);
 };
 
 /**
  * A collection of static utility methods that are only exposed to system code.
  * This is exposed in all the system globals where we can expose stuff by
  * default, so should only include methods that are **thread-safe**.
  */
-[ChromeOnly, Exposed=(Window,System,Worker)]
+[ChromeOnly, Exposed=(Window,Worker)]
 namespace ChromeUtils {
   /**
    * Serialize a snapshot of the heap graph, as seen by |JS::ubi::Node| and
    * restricted by |boundaries|, and write it to the provided file path.
    *
    * @param boundaries        The portion of the heap graph to write.
    *
    * @returns                 The path to the file the heap snapshot was written
@@ -143,17 +143,17 @@ namespace ChromeUtils {
    * IF YOU ADD NEW METHODS HERE, MAKE SURE THEY ARE THREAD-SAFE.
    */
 };
 
 /**
  * Additional ChromeUtils methods that are _not_ thread-safe, and hence not
  * exposed in workers.
  */
-[Exposed=(Window,System)]
+[Exposed=Window]
 partial namespace ChromeUtils {
   /**
    * A helper that converts OriginAttributesDictionary to a opaque suffix string.
    *
    * @param originAttrs       The originAttributes from the caller.
    */
   ByteString
   originAttributesToSuffix(optional OriginAttributesDictionary originAttrs);

--- a/dom/chrome-webidl/DominatorTree.webidl
+++ b/dom/chrome-webidl/DominatorTree.webidl
@@ -33,17 +33,17 @@ typedef unsigned long long NodeSize;
  *     the original node wasn't (directly or indirectly) referencing them. In
  *     other words, the retained size is the shallow size of a node plus the
  *     shallow sizes of every other node it dominates. For example, the root
  *     node in a binary tree might have a small shallow size that does not take
  *     up much space itself, but it dominates the rest of the binary tree and
  *     its retained size is therefore significant (assuming no external
  *     references into the tree).
  */
-[ChromeOnly, Exposed=(Window,System,Worker)]
+[ChromeOnly, Exposed=(Window,Worker)]
 interface DominatorTree {
   /**
    * The `NodeId` for the root of the dominator tree. This is a "meta-root" in
    * that it has an edge to each GC root in the heap snapshot this dominator
    * tree was created from.
    */
   readonly attribute NodeId root;
 

--- a/dom/chrome-webidl/HeapSnapshot.webidl
+++ b/dom/chrome-webidl/HeapSnapshot.webidl
@@ -2,17 +2,17 @@
 /* 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/.
  */
 
 /**
  * A HeapSnapshot represents a snapshot of the heap graph
  */
-[ChromeOnly, Exposed=(Window,System,Worker)]
+[ChromeOnly, Exposed=(Window,Worker)]
 interface HeapSnapshot {
   /**
    * A time stamp of when the heap snapshot was taken, if available. Units are
    * microseconds since midnight (00:00:00) 1 January 1970 UTC.
    */
   readonly attribute unsigned long long? creationTime;
 
   /**

--- a/dom/chrome-webidl/MatchGlob.webidl
+++ b/dom/chrome-webidl/MatchGlob.webidl
@@ -4,17 +4,17 @@
 
 /**
  * Represents a simple glob pattern matcher. Any occurrence of "*" in the glob
  * pattern matches any literal string of characters in the string being
  * compared. Additionally, if created with `allowQuestion = true`, any
  * occurrence of "?" in the glob matches any single literal character.
  */
 [Constructor(DOMString glob, optional boolean allowQuestion = true),
- ChromeOnly, Exposed=(Window,System)]
+ ChromeOnly, Exposed=Window]
 interface MatchGlob {
   /**
    * Returns true if the string matches the glob.
    */
   boolean matches(DOMString string);
 
   /**
    * The glob string this MatchGlob represents.

--- a/dom/chrome-webidl/MatchPattern.webidl
+++ b/dom/chrome-webidl/MatchPattern.webidl
@@ -25,17 +25,17 @@ interface URI;
  *      or a subdomain pattern, with "*." followed by a domain name, to match
  *      that domain name or any subdomain thereof.
  *    - <path>
  *      A glob pattern for paths to match. A "*" may appear anywhere within
  *      the path, and will match any string of characters. If no "*" appears,
  *      the URL path must exactly match the pattern path.
  */
 [Constructor(DOMString pattern, optional MatchPatternOptions options),
- ChromeOnly, Exposed=(Window,System)]
+ ChromeOnly, Exposed=Window]
 interface MatchPattern {
   /**
    * Returns true if the given URI matches the pattern.
    *
    * If explicit is true, only explicit domain matches, without wildcards, are
    * considered.
    */
   [Throws]
@@ -69,17 +69,17 @@ interface MatchPattern {
   readonly attribute DOMString pattern;
 };
 
 /**
  * A set of MatchPattern objects, which implements the MatchPattern API and
  * matches when any of its sub-patterns matches.
  */
 [Constructor(sequence<(DOMString or MatchPattern)> patterns, optional MatchPatternOptions options),
- ChromeOnly, Exposed=(Window,System)]
+ ChromeOnly, Exposed=Window]
 interface MatchPatternSet {
   /**
    * Returns true if the given URI matches any sub-pattern.
    *
    * If explicit is true, only explicit domain matches, without wildcards, are
    * considered.
    */
   [Throws]

--- a/dom/chrome-webidl/PlacesEvent.webidl
+++ b/dom/chrome-webidl/PlacesEvent.webidl
@@ -7,22 +7,22 @@ enum PlacesEventType {
   "page-visited",
   /**
    * data: PlacesBookmarkAddition. Fired whenever a bookmark
    * (or a bookmark folder/separator) is created.
    */
   "bookmark-added",
 };
 
-[ChromeOnly, Exposed=(Window,System)]
+[ChromeOnly, Exposed=Window]
 interface PlacesEvent {
   readonly attribute PlacesEventType type;
 };
 
-[ChromeOnly, Exposed=(Window,System)]
+[ChromeOnly, Exposed=Window]
 interface PlacesVisit : PlacesEvent {
   /**
    * URL of the visit.
    */
   readonly attribute DOMString url;
 
   /**
    * Id of the visit.
@@ -71,17 +71,17 @@ interface PlacesVisit : PlacesEvent {
    * and might be null if it is not known.
    */
   readonly attribute DOMString? lastKnownTitle;
 };
 
 /**
  * Base class for properties that are common to all bookmark events.
  */
-[ChromeOnly, Exposed=(Window,System)]
+[ChromeOnly, Exposed=Window]
 interface PlacesBookmark : PlacesEvent {
   /**
    * The id of the item.
    */
   readonly attribute long long id;
 
   /**
    * The id of the folder to which the item belongs.
@@ -130,17 +130,17 @@ dictionary PlacesBookmarkAdditionInit {
   required ByteString parentGuid;
   required unsigned short source;
   required long index;
   required DOMString title;
   required unsigned long long dateAdded;
   required boolean isTagging;
 };
 
-[ChromeOnly, Exposed=(Window,System), Constructor(PlacesBookmarkAdditionInit initDict)]
+[ChromeOnly, Exposed=Window, Constructor(PlacesBookmarkAdditionInit initDict)]
 interface PlacesBookmarkAddition : PlacesBookmark {
   /**
    * The item's index in the folder.
    */
   readonly attribute long index;
 
   /**
    * The title of the added item.

--- a/dom/chrome-webidl/PlacesObservers.webidl
+++ b/dom/chrome-webidl/PlacesObservers.webidl
@@ -1,23 +1,23 @@
 /* -*- Mode: IDL; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
 /* 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/.
  */
 
 callback PlacesEventCallback = void (sequence<PlacesEvent> events);
 
-[ChromeOnly, Exposed=(Window,System),
+[ChromeOnly, Exposed=Window,
  Constructor(PlacesEventCallback callback)]
 interface PlacesWeakCallbackWrapper {
 };
 
 // Global singleton which should handle all events for places.
-[ChromeOnly, Exposed=(Window,System)]
+[ChromeOnly, Exposed=Window]
 namespace PlacesObservers {
   [Throws]
   void addListener(sequence<PlacesEventType> eventTypes,
                    PlacesEventCallback listener);
   [Throws]
   void addListener(sequence<PlacesEventType> eventTypes,
                    PlacesWeakCallbackWrapper listener);
   [Throws]

--- a/dom/chrome-webidl/PrecompiledScript.webidl
+++ b/dom/chrome-webidl/PrecompiledScript.webidl
@@ -3,17 +3,17 @@
  * 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/.
  */
 
 /**
  * Represents a pre-compiled JS script, which can be repeatedly executed in
  * different globals without being re-parsed.
  */
-[ChromeOnly, Exposed=(Window,System)]
+[ChromeOnly, Exposed=Window]
 interface PrecompiledScript {
   /**
    * Executes the script in the context of, and with the security principal
    * of, the given object's global. If compiled with a return value, returns
    * the value of the script's last expression. Otherwise returns undefined.
    */
   [Throws]
   any executeInGlobal(object global);

--- a/dom/chrome-webidl/PrioEncoder.webidl
+++ b/dom/chrome-webidl/PrioEncoder.webidl
@@ -1,15 +1,15 @@
 /* -*- Mode: IDL; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
 /* 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/.
  */
 
-[ChromeOnly, Exposed=(Window,System)]
+[ChromeOnly, Exposed=Window]
 namespace PrioEncoder {
   [Throws, NewObject]
   PrioEncodedData encode(ByteString batchID, PrioParams params);
 };
 
 dictionary PrioParams {
   required boolean browserIsUserDefault;
   required boolean newTabPageEnabled;

--- a/dom/chrome-webidl/PromiseDebugging.webidl
+++ b/dom/chrome-webidl/PromiseDebugging.webidl
@@ -45,17 +45,17 @@ callback interface UncaughtRejectionObse
    * chain anymore.
    *
    * @param p A Promise that was previously left in uncaught state is
    * now caught, i.e. it is not the last in its chain anymore.
    */
   void onConsumed(object p);
 };
 
-[ChromeOnly, Exposed=(Window,System)]
+[ChromeOnly, Exposed=Window]
 interface PromiseDebugging {
   /**
    * The various functions on this interface all expect to take promises but
    * don't want the WebIDL behavior of assimilating random passed-in objects
    * into promises.  They also want to treat Promise subclass instances as
    * promises instead of wrapping them in a vanilla Promise, which is what the
    * IDL spec says to do.  So we list all our arguments as "object" instead of
    * "Promise" and check for them being a Promise internally.

--- a/dom/chrome-webidl/StructuredCloneHolder.webidl
+++ b/dom/chrome-webidl/StructuredCloneHolder.webidl
@@ -3,17 +3,17 @@
  * 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/.
  */
 
 /**
  * A holder for structured-clonable data which can itself be cloned with
  * little overhead, and deserialized into an arbitrary global.
  */
-[ChromeOnly, Exposed=(Window,System,Worker),
+[ChromeOnly, Exposed=(Window,Worker),
  /**
   * Serializes the given value to an opaque structured clone blob, and
   * returns the result.
   *
   * The serialization happens in the compartment of the given global or, if no
   * global is provided, the compartment of the data value.
   */
  Constructor(any data, optional object? global = null)]

--- a/dom/webidl/AbortController.webidl
+++ b/dom/webidl/AbortController.webidl
@@ -2,14 +2,14 @@
 /* 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/.
  *
  * The origin of this IDL file is
  * https://dom.spec.whatwg.org/#abortcontroller
  */
 
-[Constructor(), Exposed=(Window,Worker,System)]
+[Constructor(), Exposed=(Window,Worker)]
 interface AbortController {
   readonly attribute AbortSignal signal;
 
   void abort();
 };

--- a/dom/webidl/AbortSignal.webidl
+++ b/dom/webidl/AbortSignal.webidl
@@ -2,14 +2,14 @@
 /* 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/.
  *
  * The origin of this IDL file is
  * https://dom.spec.whatwg.org/#abortsignal
  */
 
-[Exposed=(Window,Worker,System)]
+[Exposed=(Window,Worker)]
 interface AbortSignal : EventTarget {
   readonly attribute boolean aborted;
 
   attribute EventHandler onabort;
 };

--- a/dom/webidl/AbstractWorker.webidl
+++ b/dom/webidl/AbstractWorker.webidl
@@ -1,10 +1,10 @@
 /* -*- Mode: IDL; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
 /* 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/.
  */
 
-[NoInterfaceObject, Exposed=(Window,Worker,System)]
+[NoInterfaceObject, Exposed=(Window,Worker)]
 interface AbstractWorker {
     attribute EventHandler onerror;
 };

--- a/dom/webidl/Console.webidl
+++ b/dom/webidl/Console.webidl
@@ -3,17 +3,17 @@
 /* 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/.
  *
  * For more information on this interface, please see
  * https://console.spec.whatwg.org/#console-namespace
  */
 
-[Exposed=(Window,Worker,WorkerDebugger,Worklet,System),
+[Exposed=(Window,Worker,WorkerDebugger,Worklet),
  ClassString="Console",
  ProtoObjectHack]
 namespace console {
 
   // NOTE: if you touch this namespace, remember to update the ConsoleInstance
   // interface as well!
 
   // Logging
@@ -141,17 +141,17 @@ dictionary ConsoleCounter {
 };
 
 dictionary ConsoleCounterError {
   DOMString label = "";
   DOMString error = "";
 };
 
 [ChromeOnly,
- Exposed=(Window,Worker,WorkerDebugger,Worklet,System)]
+ Exposed=(Window,Worker,WorkerDebugger,Worklet)]
 // This is basically a copy of the console namespace.
 interface ConsoleInstance {
   // Logging
   void assert(optional boolean condition = false, any... data);
   void clear();
   void count(optional DOMString label = "default");
   void countReset(optional DOMString label = "default");
   void debug(any... data);

--- a/dom/webidl/DOMError.webidl
+++ b/dom/webidl/DOMError.webidl
@@ -6,16 +6,16 @@
  * The origin of this IDL file is
  * http://dom.spec.whatwg.org/#domerror
  *
  * Copyright © 2012 W3C® (MIT, ERCIM, Keio), All Rights Reserved. W3C
  * liability, trademark and document use rules apply.
  */
 
 [Constructor(DOMString name, optional DOMString message = ""),
- Exposed=(Window,Worker,System)]
+ Exposed=(Window,Worker)]
 interface DOMError {
   [Constant, UseCounter]
   readonly attribute DOMString name;
 
   [Constant, UseCounter]
   readonly attribute DOMString message;
 };

--- a/dom/webidl/DOMException.webidl
+++ b/dom/webidl/DOMException.webidl
@@ -11,17 +11,17 @@
  */
 
 
 // This is the WebIDL version of nsIException.  This is mostly legacy stuff.
 
 interface StackFrame;
 
 [NoInterfaceObject,
- Exposed=(Window,Worker,System)]
+ Exposed=(Window,Worker)]
 interface ExceptionMembers
 {
   // The nsresult associated with this exception.
   readonly attribute unsigned long           result;
 
   // Filename location.  This is the location that caused the
   // error, which may or may not be a source file location.
   // For example, standard language errors would generally have
@@ -61,17 +61,17 @@ interface Exception {
   stringifier;
 };
 
 Exception implements ExceptionMembers;
 
 // XXXkhuey this is an 'exception', not an interface, but we don't have any
 // parser or codegen mechanisms for dealing with exceptions.
 [ExceptionClass,
- Exposed=(Window, Worker,System),
+ Exposed=(Window, Worker),
  Constructor(optional DOMString message = "", optional DOMString name)]
 interface DOMException {
   // The name of the error code (ie, a string repr of |result|).
   readonly attribute DOMString               name;
   // A custom message set by the thrower.
   readonly attribute DOMString               message;
   readonly attribute unsigned short code;
 

--- a/dom/webidl/DOMRequest.webidl
+++ b/dom/webidl/DOMRequest.webidl
@@ -1,27 +1,27 @@
 /* -*- Mode: IDL; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
 /* 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/. */
 
 enum DOMRequestReadyState { "pending", "done" };
 
-[Exposed=(Window,Worker,System), NoInterfaceObject]
+[Exposed=(Window,Worker), NoInterfaceObject]
 interface DOMRequestShared {
   readonly attribute DOMRequestReadyState readyState;
 
   readonly attribute any result;
   readonly attribute DOMException? error;
 
   attribute EventHandler onsuccess;
   attribute EventHandler onerror;
 };
 
-[Exposed=(Window,Worker,System)]
+[Exposed=(Window,Worker)]
 interface DOMRequest : EventTarget {
   // The [TreatNonCallableAsNull] annotation is required since then() should do
   // nothing instead of throwing errors when non-callable arguments are passed.
   // See documentation for Promise.then to see why we return "any".
   [NewObject, Throws]
   any then([TreatNonCallableAsNull] optional AnyCallback? fulfillCallback = null,
            [TreatNonCallableAsNull] optional AnyCallback? rejectCallback = null);
 

--- a/dom/webidl/DOMStringList.webidl
+++ b/dom/webidl/DOMStringList.webidl
@@ -5,14 +5,14 @@
  *
  * The origin of this IDL file is
  * http://www.w3.org/TR/2012/WD-dom-20120105/
  *
  * Copyright © 2012 W3C® (MIT, ERCIM, Keio), All Rights Reserved. W3C
  * liability, trademark and document use rules apply.
  */
 
-[Exposed=(Window,Worker,System)]
+[Exposed=(Window,Worker)]
 interface DOMStringList {
   readonly attribute unsigned long length;
   getter DOMString? item(unsigned long index);
   boolean contains(DOMString string);
 };

--- a/dom/webidl/ErrorEvent.webidl
+++ b/dom/webidl/ErrorEvent.webidl
@@ -1,15 +1,15 @@
 /* -*- Mode: IDL; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
 /* 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/. */
 
 [Constructor(DOMString type, optional ErrorEventInit eventInitDict),
- Exposed=(Window,Worker,System)]
+ Exposed=(Window,Worker)]
 interface ErrorEvent : Event
 {
   readonly attribute DOMString message;
   readonly attribute DOMString filename;
   readonly attribute unsigned long lineno;
   readonly attribute unsigned long colno;
   readonly attribute any error;
 };

--- a/dom/webidl/Event.webidl
+++ b/dom/webidl/Event.webidl
@@ -6,17 +6,17 @@
  * The origin of this IDL file is
  * http://www.w3.org/TR/2012/WD-dom-20120105/
  *
  * Copyright © 2012 W3C® (MIT, ERCIM, Keio), All Rights Reserved. W3C
  * liability, trademark and document use rules apply.
  */
 
 [Constructor(DOMString type, optional EventInit eventInitDict),
- Exposed=(Window,Worker,System), ProbablyShortLivingWrapper]
+ Exposed=(Window,Worker), ProbablyShortLivingWrapper]
 interface Event {
   [Pure]
   readonly attribute DOMString type;
   [Pure, BindingAlias="srcElement"]
   readonly attribute EventTarget? target;
   [Pure]
   readonly attribute EventTarget? currentTarget;
 

--- a/dom/webidl/EventTarget.webidl
+++ b/dom/webidl/EventTarget.webidl
@@ -21,17 +21,17 @@ dictionary EventListenerOptions {
 dictionary AddEventListenerOptions : EventListenerOptions {
   boolean passive;
   boolean once = false;
   [ChromeOnly]
   boolean wantUntrusted;
 };
 
 [Constructor,
- Exposed=(Window,Worker,WorkerDebugger,AudioWorklet,System)]
+ Exposed=(Window,Worker,WorkerDebugger,AudioWorklet)]
 interface EventTarget {
   /* Passing null for wantsUntrusted means "default behavior", which
      differs in content and chrome.  In content that default boolean
      value is true, while in chrome the default boolean value is
      false. */
   [Throws]
   void addEventListener(DOMString type,
                         EventListener? listener,
@@ -60,11 +60,11 @@ partial interface EventTarget {
   [ChromeOnly]
   EventHandler getEventHandler(DOMString type);
 };
 
 // Mozilla extension to make firing events on event targets from
 // chrome easier.  This returns the window which can be used to create
 // events to fire at this EventTarget, or null if there isn't one.
 partial interface EventTarget {
-  [ChromeOnly, Exposed=(Window,System), BinaryName="ownerGlobalForBindings"]
+  [ChromeOnly, Exposed=Window, BinaryName="ownerGlobalForBindings"]
   readonly attribute WindowProxy? ownerGlobal;
 };

--- a/dom/webidl/FileReader.webidl
+++ b/dom/webidl/FileReader.webidl
@@ -6,17 +6,17 @@
  * The origin of this IDL file is
  * https://w3c.github.io/FileAPI/#APIASynch
  *
  * Copyright © 2013 W3C® (MIT, ERCIM, Keio, Beihang), All Rights Reserved. W3C
  * liability, trademark and document use rules apply.
  */
 
 [Constructor,
- Exposed=(Window,Worker,System)]
+ Exposed=(Window,Worker)]
 interface FileReader : EventTarget {
   // async read methods
   [Throws]
   void readAsArrayBuffer(Blob blob);
   [Throws]
   void readAsBinaryString(Blob filedata);
   [Throws]
   void readAsText(Blob blob, optional DOMString label);

--- a/dom/webidl/IDBCursor.webidl
+++ b/dom/webidl/IDBCursor.webidl
@@ -9,17 +9,17 @@
 
 enum IDBCursorDirection {
     "next",
     "nextunique",
     "prev",
     "prevunique"
 };
 
-[Exposed=(Window,Worker,System)]
+[Exposed=(Window,Worker)]
 interface IDBCursor {
     readonly    attribute (IDBObjectStore or IDBIndex) source;
 
     readonly    attribute IDBCursorDirection           direction;
 
     [Throws]
     readonly    attribute any                          key;
 
@@ -37,13 +37,13 @@ interface IDBCursor {
 
     [Throws]
     void       continuePrimaryKey(any key, any primaryKey);
 
     [Throws]
     IDBRequest delete ();
 };
 
-[Exposed=(Window,Worker,System)]
+[Exposed=(Window,Worker)]
 interface IDBCursorWithValue : IDBCursor {
     [Throws]
     readonly    attribute any value;
 };

--- a/dom/webidl/IDBDatabase.webidl
+++ b/dom/webidl/IDBDatabase.webidl
@@ -5,17 +5,17 @@
  *
  * The origin of this IDL file is
  * https://dvcs.w3.org/hg/IndexedDB/raw-file/tip/Overview.html#idl-def-IDBObjectStoreParameters
  *
  * Copyright © 2012 W3C® (MIT, ERCIM, Keio), All Rights Reserved. W3C
  * liability, trademark and document use rules apply.
  */
 
-[Exposed=(Window,Worker,System)]
+[Exposed=(Window,Worker)]
 interface IDBDatabase : EventTarget {
     readonly    attribute DOMString          name;
     readonly    attribute unsigned long long version;
 
     readonly    attribute DOMStringList      objectStoreNames;
 
     [Throws]
     IDBObjectStore createObjectStore (DOMString name, optional IDBObjectStoreParameters optionalParameters);

--- a/dom/webidl/IDBFactory.webidl
+++ b/dom/webidl/IDBFactory.webidl
@@ -18,17 +18,17 @@ dictionary IDBOpenDBOptions
   StorageType storage;
 };
 
 /**
  * Interface that defines the indexedDB property on a window.  See
  * http://dvcs.w3.org/hg/IndexedDB/raw-file/tip/Overview.html#idl-def-IDBFactory
  * for more information.
  */
-[Exposed=(Window,Worker,System)]
+[Exposed=(Window,Worker)]
 interface IDBFactory {
   [Throws, NeedsCallerType]
   IDBOpenDBRequest
   open(DOMString name,
        [EnforceRange] unsigned long long version);
 
   [Throws, NeedsCallerType]
   IDBOpenDBRequest

--- a/dom/webidl/IDBFileHandle.webidl
+++ b/dom/webidl/IDBFileHandle.webidl
@@ -3,17 +3,17 @@
  * You can obtaone at http://mozilla.org/MPL/2.0/. */
 
 dictionary IDBFileMetadataParameters
 {
   boolean size = true;
   boolean lastModified = true;
 };
 
-[Exposed=(Window,System)]
+[Exposed=(Window)]
 interface IDBFileHandle : EventTarget
 {
   readonly attribute IDBMutableFile? mutableFile;
   // this is deprecated due to renaming in the spec
   readonly attribute IDBMutableFile? fileHandle; // now mutableFile
   readonly attribute FileMode mode;
   readonly attribute boolean active;
   attribute unsigned long long? location;

--- a/dom/webidl/IDBFileRequest.webidl
+++ b/dom/webidl/IDBFileRequest.webidl
@@ -1,14 +1,14 @@
 /* -*- Mode: IDL; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
 /* vim: set ts=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/. */
 
-[Exposed=(Window,System)]
+[Exposed=Window]
 interface IDBFileRequest : DOMRequest {
   readonly attribute IDBFileHandle? fileHandle;
   // this is deprecated due to renaming in the spec
   readonly attribute IDBFileHandle? lockedFile; // now fileHandle
 
   attribute EventHandler onprogress;
 };

--- a/dom/webidl/IDBIndex.webidl
+++ b/dom/webidl/IDBIndex.webidl
@@ -13,17 +13,17 @@ dictionary IDBIndexParameters {
     // <null>:   Not locale-aware, uses normal JS sorting.
     // <string>: Always sorted based on the rules of the specified
     //           locale (e.g. "en-US", etc.).
     // "auto":   Sorted by the platform default, may change based on
     //           user agent options.
     DOMString? locale = null;
 };
 
-[Exposed=(Window,Worker,System)]
+[Exposed=(Window,Worker)]
 interface IDBIndex {
     [SetterThrows]
     attribute DOMString name;
 
     readonly    attribute IDBObjectStore objectStore;
 
     [Throws]
     readonly    attribute any            keyPath;

--- a/dom/webidl/IDBKeyRange.webidl
+++ b/dom/webidl/IDBKeyRange.webidl
@@ -4,17 +4,17 @@
 /*
  * The origin of this IDL file is
  * https://dvcs.w3.org/hg/IndexedDB/raw-file/tip/Overview.html
  *
  * Copyright © 2012 W3C® (MIT, ERCIM, Keio), All Rights Reserved. W3C
  * liability, trademark and document use rules apply.
  */
 
-[Exposed=(Window,Worker,System)]
+[Exposed=(Window,Worker)]
 interface IDBKeyRange {
   [Throws]
   readonly attribute any     lower;
   [Throws]
   readonly attribute any     upper;
   [Constant]
   readonly attribute boolean lowerOpen;
   [Constant]
@@ -28,14 +28,14 @@ interface IDBKeyRange {
   [NewObject, Throws]
   static IDBKeyRange lowerBound (any lower, optional boolean open = false);
   [NewObject, Throws]
   static IDBKeyRange upperBound (any upper, optional boolean open = false);
   [NewObject, Throws]
   static IDBKeyRange bound (any lower, any upper, optional boolean lowerOpen = false, optional boolean upperOpen = false);
 };
 
-[Exposed=(Window,Worker,System),
+[Exposed=(Window,Worker),
  Func="mozilla::dom::IndexedDatabaseManager::ExperimentalFeaturesEnabled"]
 interface IDBLocaleAwareKeyRange : IDBKeyRange {
   [NewObject, Throws]
   static IDBLocaleAwareKeyRange bound (any lower, any upper, optional boolean lowerOpen = false, optional boolean upperOpen = false);
 };

--- a/dom/webidl/IDBMutableFile.webidl
+++ b/dom/webidl/IDBMutableFile.webidl
@@ -1,14 +1,14 @@
 /* -*- Mode: IDL; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
 /* 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/. */
 
-[Exposed=(Window,System)]
+[Exposed=Window]
 interface IDBMutableFile : EventTarget {
   readonly attribute DOMString name;
   readonly attribute DOMString type;
 
   readonly attribute IDBDatabase database;
 
   [Throws, UseCounter]
   IDBFileHandle open(optional FileMode mode = "readonly");

--- a/dom/webidl/IDBObjectStore.webidl
+++ b/dom/webidl/IDBObjectStore.webidl
@@ -7,17 +7,17 @@
  * https://dvcs.w3.org/hg/IndexedDB/raw-file/tip/Overview.html#idl-def-IDBObjectStore
  */
 
 dictionary IDBObjectStoreParameters {
     (DOMString or sequence<DOMString>)? keyPath = null;
     boolean                             autoIncrement = false;
 };
 
-[Exposed=(Window,Worker,System)]
+[Exposed=(Window,Worker)]
 interface IDBObjectStore {
     [SetterThrows]
     attribute DOMString name;
 
     [Throws]
     readonly    attribute any            keyPath;
 
     readonly    attribute DOMStringList  indexNames;

--- a/dom/webidl/IDBOpenDBRequest.webidl
+++ b/dom/webidl/IDBOpenDBRequest.webidl
@@ -2,14 +2,14 @@
 /* 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/.
  *
  * The origin of this IDL file is
  * https://dvcs.w3.org/hg/IndexedDB/raw-file/tip/Overview.html#idl-def-IDBOpenDBRequest
  */
 
-[Exposed=(Window,Worker,System)]
+[Exposed=(Window,Worker)]
 interface IDBOpenDBRequest : IDBRequest {
                 attribute EventHandler onblocked;
 
                 attribute EventHandler onupgradeneeded;
 };

--- a/dom/webidl/IDBRequest.webidl
+++ b/dom/webidl/IDBRequest.webidl
@@ -8,17 +8,17 @@
  * https://dvcs.w3.org/hg/IndexedDB/raw-file/tip/Overview.html#idl-def-IDBRequestReadyState
  */
 
 enum IDBRequestReadyState {
     "pending",
     "done"
 };
 
-[Exposed=(Window,Worker,System)]
+[Exposed=(Window,Worker)]
 interface IDBRequest : EventTarget {
     [Throws]
     readonly    attribute any                  result;
 
     [Throws]
     readonly    attribute DOMException?        error;
 
     readonly    attribute (IDBObjectStore or IDBIndex or IDBCursor)? source;

--- a/dom/webidl/IDBTransaction.webidl
+++ b/dom/webidl/IDBTransaction.webidl
@@ -14,17 +14,17 @@ enum IDBTransactionMode {
     // The "readwriteflush" mode is only available when the
     // |IndexedDatabaseManager::ExperimentalFeaturesEnabled()| function returns
     // true. This mode is not yet part of the standard.
     "readwriteflush",
     "cleanup",
     "versionchange"
 };
 
-[Exposed=(Window,Worker,System)]
+[Exposed=(Window,Worker)]
 interface IDBTransaction : EventTarget {
     [Throws]
     readonly    attribute IDBTransactionMode mode;
     readonly    attribute IDBDatabase        db;
 
     readonly    attribute DOMException?      error;
 
     [Throws]

--- a/dom/webidl/IDBVersionChangeEvent.webidl
+++ b/dom/webidl/IDBVersionChangeEvent.webidl
@@ -11,14 +11,14 @@
  */
 
 dictionary IDBVersionChangeEventInit : EventInit {
     unsigned long long  oldVersion = 0;
     unsigned long long? newVersion = null;
 };
 
 [Constructor(DOMString type, optional IDBVersionChangeEventInit eventInitDict),
- Exposed=(Window,Worker,System)]
+ Exposed=(Window,Worker)]
 interface IDBVersionChangeEvent : Event {
     readonly    attribute unsigned long long  oldVersion;
     readonly    attribute unsigned long long? newVersion;
 };
 

--- a/dom/webidl/IdleDeadline.webidl
+++ b/dom/webidl/IdleDeadline.webidl
@@ -2,14 +2,14 @@
 /* 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/.
  *
  * The origin of this IDL file is:
  * https://w3c.github.io/requestidlecallback/
  */
 
-[Exposed=(Window,System),
+[Exposed=Window,
  Func="nsGlobalWindowInner::IsRequestIdleCallbackEnabled"]
 interface IdleDeadline {
   DOMHighResTimeStamp timeRemaining();
   readonly attribute boolean didTimeout;
 };

--- a/dom/webidl/LegacyQueryInterface.webidl
+++ b/dom/webidl/LegacyQueryInterface.webidl
@@ -5,20 +5,20 @@
  */
 
 interface nsISupports;
 interface IID;
 
 [NoInterfaceObject,
  // Need Exposed here, because this is a mixin onto things like Event
  // that are exposed in workers.
- Exposed=(Window,Worker,System)]
+ Exposed=(Window,Worker)]
 interface LegacyQueryInterface {
   // Legacy QueryInterface, only exposed to chrome code on the main thread.
-  [Exposed=(Window,System), ChromeOnly]
+  [Exposed=Window, ChromeOnly]
   nsISupports QueryInterface(IID iid);
 };
 
 DOMParser implements LegacyQueryInterface;
 Document implements LegacyQueryInterface;
 DocumentFragment implements LegacyQueryInterface;
 Element implements LegacyQueryInterface;
 Event implements LegacyQueryInterface;

--- a/dom/webidl/MessageChannel.webidl
+++ b/dom/webidl/MessageChannel.webidl
@@ -2,13 +2,13 @@
 /* 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/.
  *
  * For more information on this interface, please see
  * http://www.whatwg.org/specs/web-apps/current-work/#channel-messaging
  */
 
-[Constructor, Exposed=(Window,Worker,System)]
+[Constructor, Exposed=(Window,Worker)]
 interface MessageChannel {
   readonly attribute MessagePort port1;
   readonly attribute MessagePort port2;
 };

--- a/dom/webidl/MessageEvent.webidl
+++ b/dom/webidl/MessageEvent.webidl
@@ -3,17 +3,17 @@
  * 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/.
  *
  * For more information on this interface, please see
  * https://html.spec.whatwg.org/#messageevent
  */
 
 [Constructor(DOMString type, optional MessageEventInit eventInitDict),
- Exposed=(Window,Worker,System)]
+ Exposed=(Window,Worker)]
 interface MessageEvent : Event {
   /**
    * Custom data associated with this event.
    */
   [GetterThrows]
   readonly attribute any data;
 
   /**

--- a/dom/webidl/MessagePort.webidl
+++ b/dom/webidl/MessagePort.webidl
@@ -2,17 +2,17 @@
 /* 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/.
  *
  * For more information on this interface, please see
  * http://www.whatwg.org/specs/web-apps/current-work/#channel-messaging
  */
 
-[Exposed=(Window,Worker,AudioWorklet,System)]
+[Exposed=(Window,Worker,AudioWorklet)]
 interface MessagePort : EventTarget {
   [Throws]
   void postMessage(any message, optional sequence<object> transferable = []);
 
   void start();
   void close();
 
   // event handlers

--- a/dom/webidl/Promise.webidl
+++ b/dom/webidl/Promise.webidl
@@ -9,12 +9,11 @@
 
 callback PromiseJobCallback = void();
 
 [TreatNonCallableAsNull]
 callback AnyCallback = any (any value);
 
 // Hack to allow us to have JS owning and properly tracing/CCing/etc a
 // PromiseNativeHandler.
-[NoInterfaceObject,
- Exposed=(Window,Worker,System)]
+[NoInterfaceObject, Exposed=(Window,Worker)]
 interface PromiseNativeHandler {
 };

--- a/dom/webidl/StreamFilter.webidl
+++ b/dom/webidl/StreamFilter.webidl
@@ -52,17 +52,17 @@ enum StreamFilterStatus {
    */
   "failed",
 };
 
 /**
  * An interface which allows an extension to intercept, and optionally modify,
  * response data from an HTTP request.
  */
-[Exposed=(Window,System),
+[Exposed=Window,
  Func="mozilla::extensions::StreamFilter::IsAllowedInContext"]
 interface StreamFilter : EventTarget {
   /**
    * Creates a stream filter for the given add-on and the given extension ID.
    */
   [ChromeOnly]
   static StreamFilter create(unsigned long long requestId, DOMString addonId);
 

--- a/dom/webidl/StreamFilterDataEvent.webidl
+++ b/dom/webidl/StreamFilterDataEvent.webidl
@@ -8,17 +8,17 @@
  * content. It allows monitoring and filtering of HTTP response stream data.
  *
  * This API should currently be considered experimental, and is not defined by
  * any standard.
  */
 
 [Constructor(DOMString type, optional StreamFilterDataEventInit eventInitDict),
  Func="mozilla::extensions::StreamFilter::IsAllowedInContext",
- Exposed=(Window,System)]
+ Exposed=Window]
 interface StreamFilterDataEvent : Event {
   /**
    * Contains a chunk of data read from the input stream.
    */
   [Pure]
   readonly attribute ArrayBuffer data;
 };
 

--- a/dom/webidl/TCPServerSocket.webidl
+++ b/dom/webidl/TCPServerSocket.webidl
@@ -10,17 +10,17 @@
  */
 
 dictionary ServerSocketOptions {
   TCPSocketBinaryType binaryType = "string";
 };
 
 [Constructor(unsigned short port, optional ServerSocketOptions options, optional unsigned short backlog = 0),
  Func="mozilla::dom::TCPSocket::ShouldTCPSocketExist",
- Exposed=(Window,System)]
+ Exposed=Window]
 interface TCPServerSocket : EventTarget {
   /**
    * The port of this server socket object.
    */
   readonly attribute unsigned short localPort;
 
   /**
    * The "connect" event is dispatched when a client connection is accepted.

--- a/dom/webidl/TCPServerSocketEvent.webidl
+++ b/dom/webidl/TCPServerSocketEvent.webidl
@@ -1,15 +1,15 @@
 /* -*- Mode: IDL; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
 /* 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/. */
 
 [Constructor(DOMString type, optional TCPServerSocketEventInit eventInitDict),
  Func="mozilla::dom::TCPSocket::ShouldTCPSocketExist",
- Exposed=(Window,System)]
+ Exposed=Window]
 interface TCPServerSocketEvent : Event {
   readonly attribute TCPSocket socket;
 };
 
 dictionary TCPServerSocketEventInit : EventInit {
   TCPSocket? socket = null;
 };

--- a/dom/webidl/TCPSocket.webidl
+++ b/dom/webidl/TCPSocket.webidl
@@ -36,17 +36,17 @@ interface LegacyMozTCPSocket {
   TCPSocket open(DOMString host, unsigned short port, optional SocketOptions options);
 
   [Throws]
   TCPServerSocket listen(unsigned short port, optional ServerSocketOptions options, optional unsigned short backlog = 0);
 };
 
 [Constructor(DOMString host, unsigned short port, optional SocketOptions options),
  Func="mozilla::dom::TCPSocket::ShouldTCPSocketExist",
- Exposed=(Window,System)]
+ Exposed=Window]
 interface TCPSocket : EventTarget {
   /**
    * Upgrade an insecure connection to use TLS. Throws if the ready state is not OPEN.
    */
   [Throws] void upgradeToSecure();
 
   /**
    * The UTF16 host of this socket object.

--- a/dom/webidl/TCPSocketErrorEvent.webidl
+++ b/dom/webidl/TCPSocketErrorEvent.webidl
@@ -6,17 +6,17 @@
 /* Dispatched as part of the "error" event in the following situations:
 * - if there's an error detected when the TCPSocket closes
 * - if there's an internal error while sending data
 * - if there's an error connecting to the host
 */
 
 [Constructor(DOMString type, optional TCPSocketErrorEventInit eventInitDict),
  Func="mozilla::dom::TCPSocket::ShouldTCPSocketExist",
- Exposed=(Window,System)]
+ Exposed=Window]
 interface TCPSocketErrorEvent : Event {
   readonly attribute DOMString name;
   readonly attribute DOMString message;
 };
 
 dictionary TCPSocketErrorEventInit : EventInit
 {
   DOMString name = "";

--- a/dom/webidl/TCPSocketEvent.webidl
+++ b/dom/webidl/TCPSocketEvent.webidl
@@ -6,17 +6,17 @@
 /**
  * TCPSocketEvent is the event dispatched for all of the events described by TCPSocket,
  * except the "error" event. It contains the socket that was associated with the event,
  * the type of event, and the data associated with the event if the event is a "data" event.
  */
 
 [Constructor(DOMString type, optional TCPSocketEventInit eventInitDict),
  Func="mozilla::dom::TCPSocket::ShouldTCPSocketExist",
- Exposed=(Window,System)]
+ Exposed=Window]
 interface TCPSocketEvent : Event {
   /**
    * If the event is a "data" event, data will be the bytes read from the network;
    * if the binaryType of the socket was "arraybuffer", this value will be of type
    * ArrayBuffer, otherwise, it will be a ByteString.
    *
    * For other events, data will be an empty string.
    */

--- a/dom/webidl/TextDecoder.webidl
+++ b/dom/webidl/TextDecoder.webidl
@@ -6,17 +6,17 @@
  * The origin of this IDL file is
  * http://encoding.spec.whatwg.org/#interface-textdecoder
  *
  * Any copyright is dedicated to the Public Domain.
  * http://creativecommons.org/publicdomain/zero/1.0/
  */
 
 [Constructor(optional DOMString label = "utf-8", optional TextDecoderOptions options),
- Exposed=(Window,Worker,System)]
+ Exposed=(Window,Worker)]
 interface TextDecoder {
   [Constant]
   readonly attribute DOMString encoding;
   [Constant]
   readonly attribute boolean fatal;
   [Constant]
   readonly attribute boolean ignoreBOM;
   [Throws]

--- a/dom/webidl/TextEncoder.webidl
+++ b/dom/webidl/TextEncoder.webidl
@@ -5,18 +5,17 @@
  *
  * The origin of this IDL file is
  * http://encoding.spec.whatwg.org/#interface-textencoder
  *
  * Any copyright is dedicated to the Public Domain.
  * http://creativecommons.org/publicdomain/zero/1.0/
  */
 
-[Constructor,
- Exposed=(Window,Worker,System)]
+[Constructor, Exposed=(Window,Worker)]
 interface TextEncoder {
   [Constant]
   readonly attribute DOMString encoding;
   /*
    * This is spec-wise USVString but marking it as
    * DOMString to avoid duplicate work. Since the
    * UTF-16 to UTF-8 converter performs processing
    * that's equivalent to first converting a

--- a/dom/webidl/URLSearchParams.webidl
+++ b/dom/webidl/URLSearchParams.webidl
@@ -9,17 +9,17 @@
  * To the extent possible under law, the editors have waived all copyright
  * and related or neighboring rights to this work. In addition, as of 17
  * February 2013, the editors have made this specification available under
  * the Open Web Foundation Agreement Version 1.0, which is available at
  * http://www.openwebfoundation.org/legal/the-owf-1-0-agreements/owfa-1-0.
  */
 
 [Constructor(optional (sequence<sequence<USVString>> or record<USVString, USVString> or USVString) init = ""),
- Exposed=(Window,Worker,WorkerDebugger,System)]
+ Exposed=(Window,Worker,WorkerDebugger)]
 interface URLSearchParams {
   void append(USVString name, USVString value);
   void delete(USVString name);
   USVString? get(USVString name);
   sequence<USVString> getAll(USVString name);
   boolean has(USVString name);
   void set(USVString name, USVString value);
 

--- a/dom/webidl/Worker.webidl
+++ b/dom/webidl/Worker.webidl
@@ -8,17 +8,17 @@
  *
  * © Copyright 2004-2011 Apple Computer, Inc., Mozilla Foundation, and Opera
  * Software ASA.
  * You are granted a license to use, reproduce and create derivative works of
  * this document.
  */
 
 [Constructor(USVString scriptURL, optional WorkerOptions options),
- Exposed=(Window,DedicatedWorker,SharedWorker,System)]
+ Exposed=(Window,DedicatedWorker,SharedWorker)]
 interface Worker : EventTarget {
   void terminate();
 
   [Throws]
   void postMessage(any message, optional sequence<object> transfer = []);
 
   attribute EventHandler onmessage;
   attribute EventHandler onmessageerror;
@@ -29,11 +29,11 @@ Worker implements AbstractWorker;
 dictionary WorkerOptions {
   // WorkerType type = "classic"; TODO: Bug 1247687
   // RequestCredentials credentials = "omit"; // credentials is only used if type is "module" TODO: Bug 1247687
   DOMString name = "";
 };
 
 [Constructor(USVString scriptURL),
  Func="mozilla::dom::ChromeWorker::WorkerAvailable",
- Exposed=(Window,DedicatedWorker,SharedWorker,System)]
+ Exposed=(Window,DedicatedWorker,SharedWorker)]
 interface ChromeWorker : Worker {
 };