Mark testSiteExceptionCookiesBlocked flaky.

TBR: dullweber@chromium.org
Bug: 1139480
Change-Id: I0413c0f7d73fe811c678e8cc290609cffab5eedd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2481823Reviewed-by: Sky Malice <skym@chromium.org>
Commit-Queue: Sky Malice <skym@chromium.org>
Cr-Commit-Position: refs/heads/master@{#818125}

chrome/android/javatests/src/org/chromium/chrome/browser/site_settings/SiteSettingsTest.java

@@ -418,6 +418,7 @@ public class SiteSettingsTest {
     // Todo(eokoyomon) figure out how to set and test third party cookie setting in this test
     // @EnableFeatures(
     //         ContentSettingsFeatureList.IMPROVED_COOKIE_CONTROLS_FOR_THIRD_PARTY_COOKIE_BLOCKING)
+    @FlakyTest(message = "https://crbug.com/1139480")
     public void testSiteExceptionCookiesBlocked() throws Exception {
         SettingsActivity settingsActivity =
                 SiteSettingsTestUtils.startSiteSettingsCategory(SiteSettingsCategory.Type.COOKIES);