Revert "Temporarily disable performance.now() in the d8 shell."

test/mjsunit/d8-performance-now.js

 // Copyright 2013 the V8 project authors. All rights reserved.
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 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
 //       with the distribution.
 //     * Neither the name of Google Inc. nor the names of its
 //       contributors may be used to endorse or promote products derived
 //       from this software without specific prior written permission.
 //
 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 // Flags: --allow-natives-syntax
 
-// The below test function was generated from part of a WebKit layout
-// test library setup routine: fast/canvas/webgl/resources/pnglib.js
+// Test the performance.now() function of d8.  This test only makes sense with
+// d8.
 
-function test(crc32) {
-  for (var i = 0; i < 256; i++) {
-    var c = i;
-    for (var j = 0; j < 8; j++) {
-      if (c & 1) {
-        c = -306674912 ^ ((c >> 1) & 0x7fffffff);
+// Don't run this test in gc stress mode. Time differences may be long
+// due to garbage collections.
+%SetFlags("--gc-interval=-1");
+%SetFlags("--nostress-compaction");
+
+if (this.performance && performance.now) {
+  (function run() {
+    var start_test = performance.now();
+    // Let the retry run for maximum 100ms to reduce flakiness.
+    for (var start = performance.now();
+        start - start_test < 100;
+        start = performance.now()) {
+      var end = performance.now();
+      assertTrue(start >= start_test);
+      assertTrue(end >= start);
+      while (end - start == 0) {
+        var next = performance.now();
+        assertTrue(next >= end);
+        end = next;
+      }
+      if (end - start <= 1) {
+        // Found (sub-)millisecond granularity.
+        return;
       } else {
-        c = (c >> 1) & 0x7fffffff;
+        print("Timer difference too big: " + (end - start) + "ms");
       }
     }
-    crc32[i] = c;
-  }
+    assertTrue(false);
+  })()
 }
-
-var a = [0.5];
-for (var i = 0; i < 256; ++i) a[i] = i;
-
-test([0.5]);
-test(a);
-%OptimizeFunctionOnNextCall(test);
-test(a);