Gracefully fail BigInt TypedArray.p.sort benchmarks.

'ref' builds might not yet have BigInt support. Instead of crashing
when the benchmark file is loaded, the benchmark now fails during
setup.

R=jgruber@chromium.org

Bug: chromium:834654
Change-Id: I2c03aeba4b6af947061504c369b5228d7b344307
Reviewed-on: https://chromium-review.googlesource.com/1019100
Commit-Queue: Simon Zünd <szuend@google.com>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52685}

test/js-perf-test/TypedArrays/sort.js

@@ -17,9 +17,12 @@ let typedArrayFloatConstructors = [
   {name: "Float64", ctor: Float64Array},
 ];
 
+// "ref" builds might not yet have BigInt support, so the benchmark fails
+// gracefully during setup (the constructor will be undefined), instead of
+// a hard fail when this file is loaded.
 let typedArrayBigIntConstructors = [
-  {name: "BigUint64", ctor: BigUint64Array},
-  {name: "BigInt64", ctor: BigInt64Array}
+  {name: "BigUint64", ctor: this["BigUint64Array"]},
+  {name: "BigInt64", ctor: this["BigInt64Array"]}
 ];
 
 function CreateBenchmarks(constructors, comparefns = []) {