Sync the IDL interfaces in core/frame/ with their many specs

Source/core/frame/WindowBase64.idl

Index: Source/core/frame/WindowBase64.idl
diff --git a/Source/core/frame/WindowBase64.idl b/Source/core/frame/WindowBase64.idl
index c5ed3a6b248d234b8d0d981a4cd0577b947f5127..fe2fe8ac2a678b6109b8a2f0f6be55330e5374cc 100644
--- a/Source/core/frame/WindowBase64.idl
+++ b/Source/core/frame/WindowBase64.idl
@@ -25,11 +25,12 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
-// http://www.whatwg.org/specs/web-apps/current-work/multipage/webappapis.html#windowbase64
+// https://html.spec.whatwg.org/#atob
 
 [
     NoInterfaceObject, // Always used on target of 'implements'
+    Exposed=(Window,Worker),
 ] interface WindowBase64 {
-    [RaisesException] DOMString btoa(DOMString string);
-    [RaisesException] DOMString atob(DOMString string);
+    [RaisesException] DOMString btoa(DOMString btoa);
+    [RaisesException] DOMString atob(DOMString atob);
 };