Bug 1486297 - Add a pref for Pointer Lock API so that user can disable it. r=smaug!

Differential Revision: https://phabricator.services.mozilla.com/D4637

--HG--
extra : moz-landing-system : lando

dom/webidl/Element.webidl

@@ -269,7 +269,7 @@ partial interface Element {
 
 // https://w3c.github.io/pointerlock/#extensions-to-the-element-interface
 partial interface Element {
-  [NeedsCallerType]
+  [NeedsCallerType, Pref="dom.pointer-lock.enabled"]
   void requestPointerLock();
 };
 

modules/libpref/init/all.js

@@ -195,6 +195,12 @@ pref("dom.enable_performance_observer", true);
 // Enable requestIdleCallback API
 pref("dom.requestIdleCallback.enabled", true);
 
+// Enable Pointer Lock API
+// This is added for accessibility purpose. When user has no way to exit
+// pointer lock (e.g. no keyboard available), they can use this pref to
+// disable the Pointer Lock API altogether.
+pref("dom.pointer-lock.enabled", true);
+
 // Whether the Gamepad API is enabled
 pref("dom.gamepad.enabled", true);
 pref("dom.gamepad.test.enabled", false);