diff -r 000000000000 -r 6474c204b198 js/src/tests/js1_8_5/extensions/file-mapped-arraybuffers.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/tests/js1_8_5/extensions/file-mapped-arraybuffers.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,40 @@
+// |reftest| skip-if(!xulRuntime.shell)
+// Any copyright is dedicated to the Public Domain.
+// http://creativecommons.org/licenses/publicdomain/
+
+function viewToString(view)
+{
+  return String.fromCharCode.apply(null, view);
+}
+
+function assertThrows(f, wantException)
+{
+    try {
+      f();
+      assertEq(true, false, "expected " + wantException + " exception");
+    } catch (e) {
+      assertEq(e.name, wantException.name, e.toString());
+    }
+}
+
+function test() {
+    var filename = "file-mapped-arraybuffers.txt";
+    var buffer = createMappedArrayBuffer(filename);
+    var view = new Uint8Array(buffer);
+    assertEq(viewToString(view), "01234567abcdefghijkl");
+
+    var buffer2 = createMappedArrayBuffer(filename, 8);
+    view = new Uint8Array(buffer2);
+    assertEq(viewToString(view), "abcdefghijkl");
+
+    var buffer3 = createMappedArrayBuffer(filename, 0, 8);
+    view = new Uint8Array(buffer3);
+    assertEq(viewToString(view), "01234567");
+
+    // Check that invalid sizes and offsets are caught
+    assertThrows(() => createMappedArrayBuffer("empty.txt", 8), RangeError);
+    assertThrows(() => createMappedArrayBuffer("empty.txt", 0, 8), Error);
+}
+
+test();
+reportCompare(0, 0, 'ok');