Revert of Disable slow...

Revert of Disable slow BootstrapSandboxTest.DistributedNotifications_SandboxDeny (patchset #1 of https://codereview.chromium.org/498193002/)

Reason for revert:
Unclear reason for disable.

Original issue's description:
> Disable slow BootstrapSandboxTest.DistributedNotifications_SandboxDeny
>
> TBR=rsesek
>
> BUG=407066
>
> Committed to pending queue: https://chromium.googlesource.com/chromium/src/+/f1bd7f7

TBR=phajdan.jr@chromium.org
BUG=407066

Review URL: https://codereview.chromium.org/508873003

Cr-Commit-Position: refs/heads/master@{#292207}

sandbox/mac/bootstrap_sandbox_unittest.mm

@@ -134,8 +134,7 @@ TEST_F(BootstrapSandboxTest, DistributedNotifications_Unsandboxed) {
 
 // Run the test with the sandbox enabled without notifications on the policy
 // whitelist.
-// Disabled, http://crbug.com/407066 .
-TEST_F(BootstrapSandboxTest, DISABLED_DistributedNotifications_SandboxDeny) {
+TEST_F(BootstrapSandboxTest, DistributedNotifications_SandboxDeny) {
   base::scoped_nsobject<DistributedNotificationObserver> observer(
       [[DistributedNotificationObserver alloc] init]);