Revert of Remove SIMD.js from V8.

test/perf.isolate

 # Copyright 2016 the V8 project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 {
   'variables': {
     'command': [
       '../tools/run_perf.py',
     ],
     'files': [
       '../tools/run_perf.py',
       # TODO(machenbach): These files are referenced by the perf runner.
       # They should be transformed into a proper python module.
       '../tools/testrunner/local/commands.py',
       '../tools/testrunner/local/utils.py',
       '../tools/testrunner/objects/output.py',
       # This is often used to trigger performance bots. We include it in the
       # isolate to not get these builds deduped.
       '../tools/whitespace.txt',
       'js-perf-test/',
       'memory/',
+      'simdjs/',
     ],
   },
   'includes': [
     'cctest/cctest_exe.isolate',
     '../src/d8.isolate',
   ],
 }