Speculatively enable OAuth2Test.MergeSession

Supposed to be fixed

TBR=antrim@chromium.org

Bug: 1003772
Change-Id: If9f00577aced44ddf0de36c89e5961a3d152a300
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1890037Reviewed-by: Roman Sorokin [CET] <rsorokin@chromium.org>
Commit-Queue: Roman Sorokin [CET] <rsorokin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#710760}

chrome/browser/chromeos/login/signin/oauth2_browsertest.cc

@@ -563,8 +563,7 @@ IN_PROC_BROWSER_TEST_F(OAuth2Test, PRE_MergeSession) {
 // MergeSession test is attempting to merge session for an existing profile
 // that was generated in PRE_PRE_MergeSession test. This attempt should fail
 // since FakeGaia instance isn't configured to return relevant tokens/cookies.
-// Disabling because of flakiness. Details in crbug.com/1003772.
-IN_PROC_BROWSER_TEST_F(OAuth2Test, DISABLED_MergeSession) {
+IN_PROC_BROWSER_TEST_F(OAuth2Test, MergeSession) {
   SimulateNetworkOnline();
 
   test::OobeJS().ExpectTrue("!!document.querySelector('#account-picker')");