Enabled GetReferrerChainForNonSafeBrowsingUser

This test became flaky due to an uninitialized variable introduced by
https://chromium-review.googlesource.com/c/chromium/src/+/2249162

This was fixed by
https://chromium-review.googlesource.com/c/chromium/src/+/2253759

Fixed: 1096975
Change-Id: I659848f1bb82b30f3debd4370a1b6640b72c12a1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2254349
Auto-Submit: Daniel Rubery <drubery@chromium.org>
Commit-Queue: Bettina Dea <bdea@chromium.org>
Reviewed-by: Bettina Dea <bdea@chromium.org>
Cr-Commit-Position: refs/heads/master@{#781450}

chrome/browser/extensions/api/safe_browsing_private/safe_browsing_private_api_unittest.cc

@@ -142,9 +142,7 @@ TEST_F(SafeBrowsingPrivateApiUnitTest, GetReferrerChain) {
   ASSERT_TRUE(referrer_chain);
 }
 
-// Flaky (crbug.com/1096975)
-TEST_F(SafeBrowsingPrivateApiUnitTest,
-       DISABLED_GetReferrerChainForNonSafeBrowsingUser) {
+TEST_F(SafeBrowsingPrivateApiUnitTest, GetReferrerChainForNonSafeBrowsingUser) {
   // Disable Safe Browsing.
   browser()->profile()->GetPrefs()->SetBoolean(prefs::kSafeBrowsingEnabled,
                                                false);