[foozzie] Disable optimizations for typed float arrays.

This disables optimizations when using typed float arrays in
correctness fuzzer test cases. Otherwise, different NaN patterns
in float typed arrays might lead to different observations when
using the buffer in an int array view.

BUG=chromium:683579
NOTRY=true
TBR=Jarin, mvstanton, Igor Sheludko

Review-Url: https://codereview.chromium.org/2649923008
Cr-Commit-Position: refs/heads/master@{#42626}

tools/foozzie/v8_mock.js

@@ -58,6 +58,21 @@ Error.prepareStackTrace = function (error, structuredStackTrace) {
   return "";
 }
 
+// Mock buffer access in float typed arrays because of varying NaN patterns.
+// Note, for now we just use noop forwarding proxies, because they already
+// turn off optimizations.
+function __MockTypedArray(arrayType) {
+  array_creation_handler = {
+    construct: function(target, args) {
+      return new Proxy(new arrayType(args), {});
+    },
+  };
+  return new Proxy(arrayType, array_creation_handler);
+}
+
+Float32Array = __MockTypedArray(Float32Array);
+Float64Array = __MockTypedArray(Float64Array);
+
 // Mock Worker.
 var __magic_index_for_mocked_worker = 0
 // TODO(machenbach): Randomize this for each test case, but keep stable during