Remove Cirrus CI from Flutter goldens. (#161396)

Towards https://github.com/flutter/flutter/issues/161387.

I believe this effectively a NOP as the `CIRRUS_`-environment variables
are never set.
diff --git a/packages/flutter_goldens/lib/flutter_goldens.dart b/packages/flutter_goldens/lib/flutter_goldens.dart
index 94b0199..831ef65 100644
--- a/packages/flutter_goldens/lib/flutter_goldens.dart
+++ b/packages/flutter_goldens/lib/flutter_goldens.dart
@@ -89,9 +89,8 @@
   } else if (FlutterSkippingFileComparator.isForEnvironment(platform)) {
     goldenFileComparator = FlutterSkippingFileComparator.fromLocalFileComparator(
       localFileComparator: goldenFileComparator as LocalFileComparator,
-      'Golden file testing is not executed on Cirrus, or LUCI environments '
-      'outside of flutter/flutter, or in test shards that are not configured '
-      'for using goldctl.',
+      'Golden file testing is not executed on LUCI environments outside of '
+      'flutter, or in test shards that are not configured for using goldctl.',
       platform: platform,
       namePrefix: namePrefix,
       log: print,
@@ -448,7 +447,7 @@
 /// A [FlutterGoldenFileComparator] for testing conditions that do not execute
 /// golden file tests.
 ///
-/// Currently, this comparator is used on Cirrus, or in Luci environments when executing tests
+/// Currently, this comparator is used on Luci environments when executing tests
 /// outside of the flutter/flutter repository.
 ///
 /// See also:
@@ -521,14 +520,11 @@
   /// Decides, based on the current environment, if this comparator should be
   /// used.
   ///
-  /// If we are in a CI environment, LUCI or Cirrus, but are not using the other
+  /// If we are in a CI environment, i.e. LUCI, but are not using the other
   /// comparators, we skip. Otherwise we would fallback to the local comparator,
   /// for which failures cannot be resolved in a CI environment.
   static bool isForEnvironment(Platform platform) {
-    return platform.environment.containsKey('SWARMING_TASK_ID')
-        // Some builds are still being run on Cirrus, we should skip these.
-        ||
-        platform.environment.containsKey('CIRRUS_CI');
+    return platform.environment.containsKey('SWARMING_TASK_ID');
   }
 }
 
diff --git a/packages/flutter_goldens/test/comparator_selection_test.dart b/packages/flutter_goldens/test/comparator_selection_test.dart
index 3c56b3c..d1c98f5 100644
--- a/packages/flutter_goldens/test/comparator_selection_test.dart
+++ b/packages/flutter_goldens/test/comparator_selection_test.dart
@@ -11,7 +11,6 @@
 _Comparator _testRecommendations({
   bool hasFlutterRoot = false,
   bool hasLuci = false,
-  bool hasCirrus = false,
   bool hasGold = false,
   bool hasTryJob = false,
   String branch = 'main',
@@ -21,11 +20,7 @@
     environment: <String, String>{
       if (hasFlutterRoot) 'FLUTTER_ROOT': '/flutter',
       if (hasLuci) 'SWARMING_TASK_ID': '8675309',
-      if (hasCirrus) 'CIRRUS_CI': 'true',
-      if (hasCirrus) 'CIRRUS_PR': '',
-      if (hasCirrus) 'CIRRUS_BRANCH': branch,
       if (hasGold) 'GOLDCTL': 'goldctl',
-      if (hasGold && hasCirrus) 'GOLD_SERVICE_ACCOUNT': 'service account...',
       if (hasTryJob) 'GOLD_TRYJOB': 'git/ref/12345/head',
       'GIT_BRANCH': branch,
     },
@@ -54,71 +49,25 @@
     // If we don't have gold but are on CI, we skip regardless.
     expect(_testRecommendations(hasLuci: true), _Comparator.skip);
     expect(_testRecommendations(hasLuci: true, hasTryJob: true), _Comparator.skip);
-    expect(_testRecommendations(hasCirrus: true), _Comparator.skip);
-    expect(_testRecommendations(hasCirrus: true, hasTryJob: true), _Comparator.skip);
-    expect(_testRecommendations(hasLuci: true, hasCirrus: true), _Comparator.skip);
-    expect(_testRecommendations(hasLuci: true, hasCirrus: true, hasTryJob: true), _Comparator.skip);
     expect(_testRecommendations(hasFlutterRoot: true, hasLuci: true), _Comparator.skip);
     expect(
       _testRecommendations(hasFlutterRoot: true, hasLuci: true, hasTryJob: true),
       _Comparator.skip,
     );
-    expect(_testRecommendations(hasFlutterRoot: true, hasCirrus: true), _Comparator.skip);
-    expect(
-      _testRecommendations(hasFlutterRoot: true, hasCirrus: true, hasTryJob: true),
-      _Comparator.skip,
-    );
-    expect(
-      _testRecommendations(hasFlutterRoot: true, hasLuci: true, hasCirrus: true),
-      _Comparator.skip,
-    );
-    expect(
-      _testRecommendations(hasFlutterRoot: true, hasLuci: true, hasCirrus: true, hasTryJob: true),
-      _Comparator.skip,
-    );
 
-    // On Luci, with Gold, post-submit. Flutter root and Cirrus variables should have no effect.
+    // On Luci, with Gold, post-submit. Flutter root and LUCI variables should have no effect.
     expect(_testRecommendations(hasGold: true, hasLuci: true), _Comparator.post);
-    expect(_testRecommendations(hasGold: true, hasLuci: true, hasCirrus: true), _Comparator.post);
     expect(
       _testRecommendations(hasGold: true, hasLuci: true, hasFlutterRoot: true),
       _Comparator.post,
     );
-    expect(
-      _testRecommendations(hasGold: true, hasLuci: true, hasFlutterRoot: true, hasCirrus: true),
-      _Comparator.post,
-    );
 
-    // On Luci, with Gold, pre-submit. Flutter root and Cirrus variables should have no effect.
+    // On Luci, with Gold, pre-submit. Flutter root and LUCI variables should have no effect.
     expect(_testRecommendations(hasGold: true, hasLuci: true, hasTryJob: true), _Comparator.pre);
     expect(
-      _testRecommendations(hasGold: true, hasLuci: true, hasCirrus: true, hasTryJob: true),
-      _Comparator.pre,
-    );
-    expect(
       _testRecommendations(hasGold: true, hasLuci: true, hasFlutterRoot: true, hasTryJob: true),
       _Comparator.pre,
     );
-    expect(
-      _testRecommendations(
-        hasGold: true,
-        hasLuci: true,
-        hasFlutterRoot: true,
-        hasCirrus: true,
-        hasTryJob: true,
-      ),
-      _Comparator.pre,
-    );
-
-    // On Cirrus (with Gold and not on Luci), we skip regardless.
-    expect(
-      _testRecommendations(hasCirrus: true, hasGold: true, hasFlutterRoot: true),
-      _Comparator.skip,
-    );
-    expect(
-      _testRecommendations(hasCirrus: true, hasGold: true, hasFlutterRoot: true, hasTryJob: true),
-      _Comparator.skip,
-    );
   });
 
   test('Comparator recommendations - release branch', () {
@@ -147,27 +96,6 @@
       _Comparator.skip,
     );
     expect(
-      _testRecommendations(branch: 'flutter-3.16-candidate.0', hasCirrus: true),
-      _Comparator.skip,
-    );
-    expect(
-      _testRecommendations(branch: 'flutter-3.16-candidate.0', hasCirrus: true, hasTryJob: true),
-      _Comparator.skip,
-    );
-    expect(
-      _testRecommendations(branch: 'flutter-3.16-candidate.0', hasLuci: true, hasCirrus: true),
-      _Comparator.skip,
-    );
-    expect(
-      _testRecommendations(
-        branch: 'flutter-3.16-candidate.0',
-        hasLuci: true,
-        hasCirrus: true,
-        hasTryJob: true,
-      ),
-      _Comparator.skip,
-    );
-    expect(
       _testRecommendations(branch: 'flutter-3.16-candidate.0', hasFlutterRoot: true, hasLuci: true),
       _Comparator.skip,
     );
@@ -180,44 +108,8 @@
       ),
       _Comparator.skip,
     );
-    expect(
-      _testRecommendations(
-        branch: 'flutter-3.16-candidate.0',
-        hasFlutterRoot: true,
-        hasCirrus: true,
-      ),
-      _Comparator.skip,
-    );
-    expect(
-      _testRecommendations(
-        branch: 'flutter-3.16-candidate.0',
-        hasFlutterRoot: true,
-        hasCirrus: true,
-        hasTryJob: true,
-      ),
-      _Comparator.skip,
-    );
-    expect(
-      _testRecommendations(
-        branch: 'flutter-3.16-candidate.0',
-        hasFlutterRoot: true,
-        hasLuci: true,
-        hasCirrus: true,
-      ),
-      _Comparator.skip,
-    );
-    expect(
-      _testRecommendations(
-        branch: 'flutter-3.16-candidate.0',
-        hasFlutterRoot: true,
-        hasLuci: true,
-        hasCirrus: true,
-        hasTryJob: true,
-      ),
-      _Comparator.skip,
-    );
 
-    // On Luci, with Gold, post-submit. Flutter root and Cirrus variables should have no effect. Branch should make us skip.
+    // On Luci, with Gold, post-submit. Flutter root and LUCI variables should have no effect. Branch should make us skip.
     expect(
       _testRecommendations(branch: 'flutter-3.16-candidate.0', hasGold: true, hasLuci: true),
       _Comparator.skip,
@@ -227,31 +119,12 @@
         branch: 'flutter-3.16-candidate.0',
         hasGold: true,
         hasLuci: true,
-        hasCirrus: true,
-      ),
-      _Comparator.skip,
-    );
-    expect(
-      _testRecommendations(
-        branch: 'flutter-3.16-candidate.0',
-        hasGold: true,
-        hasLuci: true,
         hasFlutterRoot: true,
       ),
       _Comparator.skip,
     );
-    expect(
-      _testRecommendations(
-        branch: 'flutter-3.16-candidate.0',
-        hasGold: true,
-        hasLuci: true,
-        hasFlutterRoot: true,
-        hasCirrus: true,
-      ),
-      _Comparator.skip,
-    );
 
-    // On Luci, with Gold, pre-submit. Flutter root and Cirrus variables should have no effect. Branch should make us skip.
+    // On Luci, with Gold, pre-submit. Flutter root and LUCI variables should have no effect. Branch should make us skip.
     expect(
       _testRecommendations(
         branch: 'flutter-3.16-candidate.0',
@@ -266,48 +139,6 @@
         branch: 'flutter-3.16-candidate.0',
         hasGold: true,
         hasLuci: true,
-        hasCirrus: true,
-        hasTryJob: true,
-      ),
-      _Comparator.skip,
-    );
-    expect(
-      _testRecommendations(
-        branch: 'flutter-3.16-candidate.0',
-        hasGold: true,
-        hasLuci: true,
-        hasFlutterRoot: true,
-        hasTryJob: true,
-      ),
-      _Comparator.skip,
-    );
-    expect(
-      _testRecommendations(
-        branch: 'flutter-3.16-candidate.0',
-        hasGold: true,
-        hasLuci: true,
-        hasFlutterRoot: true,
-        hasCirrus: true,
-        hasTryJob: true,
-      ),
-      _Comparator.skip,
-    );
-
-    // On Cirrus (with Gold and not on Luci), we skip regardless.
-    expect(
-      _testRecommendations(
-        branch: 'flutter-3.16-candidate.0',
-        hasCirrus: true,
-        hasGold: true,
-        hasFlutterRoot: true,
-      ),
-      _Comparator.skip,
-    );
-    expect(
-      _testRecommendations(
-        branch: 'flutter-3.16-candidate.0',
-        hasCirrus: true,
-        hasGold: true,
         hasFlutterRoot: true,
         hasTryJob: true,
       ),
@@ -328,13 +159,6 @@
     // If we don't have gold but are on CI, we skip regardless.
     expect(_testRecommendations(os: 'linux', hasLuci: true), _Comparator.skip);
     expect(_testRecommendations(os: 'linux', hasLuci: true, hasTryJob: true), _Comparator.skip);
-    expect(_testRecommendations(os: 'linux', hasCirrus: true), _Comparator.skip);
-    expect(_testRecommendations(os: 'linux', hasCirrus: true, hasTryJob: true), _Comparator.skip);
-    expect(_testRecommendations(os: 'linux', hasLuci: true, hasCirrus: true), _Comparator.skip);
-    expect(
-      _testRecommendations(os: 'linux', hasLuci: true, hasCirrus: true, hasTryJob: true),
-      _Comparator.skip,
-    );
     expect(
       _testRecommendations(os: 'linux', hasFlutterRoot: true, hasLuci: true),
       _Comparator.skip,
@@ -343,51 +167,15 @@
       _testRecommendations(os: 'linux', hasFlutterRoot: true, hasLuci: true, hasTryJob: true),
       _Comparator.skip,
     );
-    expect(
-      _testRecommendations(os: 'linux', hasFlutterRoot: true, hasCirrus: true),
-      _Comparator.skip,
-    );
-    expect(
-      _testRecommendations(os: 'linux', hasFlutterRoot: true, hasCirrus: true, hasTryJob: true),
-      _Comparator.skip,
-    );
-    expect(
-      _testRecommendations(os: 'linux', hasFlutterRoot: true, hasLuci: true, hasCirrus: true),
-      _Comparator.skip,
-    );
-    expect(
-      _testRecommendations(
-        os: 'linux',
-        hasFlutterRoot: true,
-        hasLuci: true,
-        hasCirrus: true,
-        hasTryJob: true,
-      ),
-      _Comparator.skip,
-    );
 
     // On Luci, with Gold, post-submit. Flutter root and Cirrus variables should have no effect.
     expect(_testRecommendations(os: 'linux', hasGold: true, hasLuci: true), _Comparator.post);
     expect(
-      _testRecommendations(os: 'linux', hasGold: true, hasLuci: true, hasCirrus: true),
-      _Comparator.post,
-    );
-    expect(
       _testRecommendations(os: 'linux', hasGold: true, hasLuci: true, hasFlutterRoot: true),
       _Comparator.post,
     );
-    expect(
-      _testRecommendations(
-        os: 'linux',
-        hasGold: true,
-        hasLuci: true,
-        hasFlutterRoot: true,
-        hasCirrus: true,
-      ),
-      _Comparator.post,
-    );
 
-    // On Luci, with Gold, pre-submit. Flutter root and Cirrus variables should have no effect.
+    // On Luci, with Gold, pre-submit. Flutter root should have no effect.
     expect(
       _testRecommendations(os: 'linux', hasGold: true, hasLuci: true, hasTryJob: true),
       _Comparator.pre,
@@ -397,48 +185,11 @@
         os: 'linux',
         hasGold: true,
         hasLuci: true,
-        hasCirrus: true,
-        hasTryJob: true,
-      ),
-      _Comparator.pre,
-    );
-    expect(
-      _testRecommendations(
-        os: 'linux',
-        hasGold: true,
-        hasLuci: true,
         hasFlutterRoot: true,
         hasTryJob: true,
       ),
       _Comparator.pre,
     );
-    expect(
-      _testRecommendations(
-        os: 'linux',
-        hasGold: true,
-        hasLuci: true,
-        hasFlutterRoot: true,
-        hasCirrus: true,
-        hasTryJob: true,
-      ),
-      _Comparator.pre,
-    );
-
-    // On Cirrus (with Gold and not on Luci), we skip regardless.
-    expect(
-      _testRecommendations(os: 'linux', hasCirrus: true, hasGold: true, hasFlutterRoot: true),
-      _Comparator.skip,
-    );
-    expect(
-      _testRecommendations(
-        os: 'linux',
-        hasCirrus: true,
-        hasGold: true,
-        hasFlutterRoot: true,
-        hasTryJob: true,
-      ),
-      _Comparator.skip,
-    );
   });
 
   test('Branch names', () {