Add DOMSharedArrayBuffer type

Source/core/dom/SharedArrayBuffer.idl

Index: Source/core/dom/SharedArrayBuffer.idl
diff --git a/Source/core/dom/ArrayBuffer.idl b/Source/core/dom/SharedArrayBuffer.idl
similarity index 53%
copy from Source/core/dom/ArrayBuffer.idl
copy to Source/core/dom/SharedArrayBuffer.idl
index 12c506b725dbbdf349127840d66fa61dc1309513..21bb64b3d59f4f364d3aab4f423eeb58474ecd07 100644
--- a/Source/core/dom/ArrayBuffer.idl
+++ b/Source/core/dom/SharedArrayBuffer.idl
@@ -2,11 +2,13 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// https://www.khronos.org/registry/typedarray/specs/latest/#ARRAYBUFFER
+// Draft spec:
+// https://docs.google.com/document/d/1NDGA_gZJ7M7w1Bh8S0AoDyEqwDdRh4uSoTPSNn77PFk
 
 [
-    ImplementedAs=DOMArrayBuffer,
+    ImplementedAs=DOMSharedArrayBuffer,
     NoInterfaceObject,
-] interface ArrayBuffer {
+    RuntimeEnabled=SharedArrayBuffer,
+] interface SharedArrayBuffer {
     readonly attribute unsigned long byteLength;
 };