Add bit-precision tests for TypedArray#copyWithin

test/built-ins/TypedArray/prototype/copyWithin/bit-precision.js

@@ -0,0 +1,44 @@
+// Copyright (C) 2016 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-%typedarray%.prototype.copywithin
+es6id: 22.2.3.5
+description: Preservation of bit-level encoding
+info: |
+  Array.prototype.copyWithin (target, start [ , end ] )
+
+  12. Repeat, while count > 0
+    [...]
+    d. If fromPresent is true, then
+      i. Let fromVal be ? Get(O, fromKey).
+      ii. Perform ? Set(O, toKey, fromVal, true).
+includes: [nans.js, compareArray.js, testTypedArray.js]
+---*/
+
+function body(FloatArray) {
+  var subject = new FloatArray(distinctNaNs.length * 2);
+
+  distinctNaNs.forEach(function(v, i) {
+    subject[i] = v;
+  });
+
+  var originalBytes, copiedBytes;
+  var length = distinctNaNs.length * FloatArray.BYTES_PER_ELEMENT;
+
+  originalBytes = new Uint8Array(
+    subject.buffer,
+    0,
+    length
+  );
+
+  subject.copyWithin(distinctNaNs.length, 0);
+  copiedBytes = new Uint8Array(
+    subject.buffer,
+    length
+  );
+
+  assert(compareArray(originalBytes, copiedBytes));
+}
+
+testWithTypedArrayConstructors(body, [Float32Array, Float64Array]);