[IOS][UKM] Fix and enable UKM EG tests on iOS

UKM EG tests were failing on iOS because the signed in account was staying
around after signing out causing EG selector to fail to tap on the
appropriate account in subsequent sign in attempts. This CL fixes that by
removing the signed in account when signing out.

Bug: 853992
Cq-Include-Trybots: luci.chromium.try:ios-simulator-full-configs;master.tryserver.chromium.mac:ios-simulator-cronet
Change-Id: I77ec271bbb694766b6487be52ec4e3a18f7839d4
Reviewed-on: https://chromium-review.googlesource.com/1146986Reviewed-by: Olivier Robin <olivierrobin@chromium.org>
Commit-Queue: Moe Ahmadi <mahmadi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#577511}

ios/chrome/browser/metrics/ukm_egtest.mm

@@ -38,6 +38,7 @@
 #endif
 
 using chrome_test_util::AccountsSyncButton;
+using chrome_test_util::ButtonWithAccessibilityLabel;
 using chrome_test_util::ButtonWithAccessibilityLabelId;
 using chrome_test_util::ClearBrowsingDataCollectionView;
 using chrome_test_util::GetIncognitoTabCount;
@@ -194,13 +195,17 @@ void UpdateMetricsConsent(bool new_state) {
 // Signs out of sync.
 void SignOut() {
   [ChromeEarlGreyUI openSettingsMenu];
-  [[EarlGrey selectElementWithMatcher:SettingsAccountButton()]
+  [ChromeEarlGreyUI tapSettingsMenuButton:SettingsAccountButton()];
+
+  // Remove |identity| from the device.
+  ChromeIdentity* identity = [SigninEarlGreyUtils fakeIdentity1];
+  [[EarlGrey
+      selectElementWithMatcher:ButtonWithAccessibilityLabel(identity.userEmail)]
       performAction:grey_tap()];
-  [ChromeEarlGreyUI tapAccountsMenuButton:SignOutAccountsButton()];
-  [[EarlGrey selectElementWithMatcher:
-                 ButtonWithAccessibilityLabelId(
-                     IDS_IOS_DISCONNECT_DIALOG_CONTINUE_BUTTON_MOBILE)]
+  [[EarlGrey
+      selectElementWithMatcher:ButtonWithAccessibilityLabel(@"Remove account")]
       performAction:grey_tap()];
+
   [[EarlGrey selectElementWithMatcher:SettingsDoneButton()]
       performAction:grey_tap()];
 
@@ -216,11 +221,6 @@ void SignOut() {
 
 @implementation UKMTestCase
 
-// Per crbug.com/853992, Entire test suite is failing regularly.
-+ (NSArray*)testInvocations {
-  return @[];
-}
-
 + (void)setUp {
   [super setUp];
   if (!base::FeatureList::IsEnabled(ukm::kUkmFeature)) {
@@ -466,7 +466,8 @@ void SignOut() {
 
 // testMetricsReporting not needed, since iOS doesn't use sampling.
 
-- (void)testHistoryDelete {
+// TODO(crbug.com/866598): Re-enable this test.
+- (void)DISABLED_testHistoryDelete {
   uint64_t original_client_id = metrics::UkmEGTestHelper::client_id();
 
   const ukm::SourceId kDummySourceId = 0x54321;