Use flutter repo for engine golds instead of flutter-engine. (#160556)

Closes https://github.com/flutter/flutter/issues/157206.

I also added a `prefix` that will default to `engine.` to avoid
accidentally stomping on golden names across repos.

/cc @gaaclarke for visibility, @Piinks for visibility.

(I would love to get rid of this "engine copy" of the client as part of
longer-term mono repo deduplication).

engine/src/flutter/testing/dart/canvas_test.dart

@@ -173,7 +173,7 @@ String get _flutterBuildPath {
 }
 
 void main() async {
-  final ImageComparer comparer = await ImageComparer.create();
+  final ImageComparer comparer = await ImageComparer.create(verbose: true);
 
   testNoCrashes();
 

engine/src/flutter/testing/skia_gold_client/lib/skia_gold_client.dart

@@ -20,8 +20,8 @@ const String _kGoldctlKey = 'GOLDCTL';
 const String _kPresubmitEnvName = 'GOLD_TRYJOB';
 const String _kLuciEnvName = 'LUCI_CONTEXT';
 
-const String _skiaGoldHost = 'https://flutter-engine-gold.skia.org';
+const String _skiaGoldHost = 'https://flutter-gold.skia.org';
-const String _instance = 'flutter-engine';
+const String _instance = 'flutter';
 
 /// Uploads images and makes baseline requests to Skia Gold.
 ///
@@ -47,10 +47,16 @@ interface class SkiaGoldClient {
   /// spammy for regular use.
   factory SkiaGoldClient(
     io.Directory workDirectory, {
+    String prefix = 'engine.',
     Map<String, String>? dimensions,
     bool verbose = false,
   }) {
-    return SkiaGoldClient.forTesting(workDirectory, dimensions: dimensions, verbose: verbose);
+    return SkiaGoldClient.forTesting(
+      workDirectory,
+      dimensions: dimensions,
+      verbose: verbose,
+      prefix: prefix,
+    );
   }
 
   /// Creates a [SkiaGoldClient] for testing.
@@ -73,6 +79,7 @@ interface class SkiaGoldClient {
     this.workDirectory, {
     this.dimensions,
     this.verbose = false,
+    String? prefix,
     io.HttpClient? httpClient,
     ProcessManager? processManager,
     StringSink? stderr,
@@ -80,6 +87,7 @@ interface class SkiaGoldClient {
     Engine? engineRoot,
   }) : httpClient = httpClient ?? io.HttpClient(),
        process = processManager ?? const LocalProcessManager(),
+       _prefix = prefix,
        _stderr = stderr ?? io.stderr,
        _environment = environment ?? io.Platform.environment,
        _engineRoot = engineRoot ?? Engine.findWithin() {
@@ -166,6 +174,9 @@ interface class SkiaGoldClient {
   /// client will create image and JSON files for the `goldctl` tool to use.
   final io.Directory workDirectory;
 
+  /// Prefix to add to all test names, if any.
+  final String? _prefix;
+
   String get _tempPath => path.join(workDirectory.path, 'temp');
   String get _keysPath => path.join(workDirectory.path, 'keys.json');
   String get _failuresPath => path.join(workDirectory.path, 'failures.json');
@@ -345,6 +356,11 @@ interface class SkiaGoldClient {
     // Clean the test name to remove the file extension.
     testName = path.basenameWithoutExtension(testName);
 
+    // Add a prefix to avoid repo-wide conflicts.
+    if (_prefix != null) {
+      testName = '$_prefix$testName';
+    }
+
     // In release branches, we add a unique test suffix to the test name.
     // For example "testName" -> "testName_Release_3_21".
     // See ../README.md#release-testing for more information.
@@ -408,7 +424,7 @@ interface class SkiaGoldClient {
             ..writeln('testing. Golden file images in flutter/engine are triaged ')
             ..writeln('in pre-submit during code review for the given PR.')
             ..writeln()
-            ..writeln('Visit https://flutter-engine-gold.skia.org/ to view and approve ')
+            ..writeln('Visit https://flutter-gold.skia.org/ to view and approve ')
             ..writeln('the image(s), or revert the associated change. For more ')
             ..writeln('information, visit the wiki: ')
             ..writeln(

engine/src/flutter/testing/skia_gold_client/test/skia_gold_client_test.dart

@@ -22,7 +22,7 @@ void main() {
   const Map<String, String> presubmitEnv = <String, String>{
     'GIT_BRANCH': 'master',
     'GOLDCTL': 'python tools/goldctl.py',
-    'GOLD_TRYJOB': 'flutter/engine/1234567890',
+    'GOLD_TRYJOB': 'flutter/flutter/1234567890',
     'LOGDOG_STREAM_PREFIX': 'buildbucket/cr-buildbucket.appspot.com/1234567890/+/logdog',
     'LUCI_CONTEXT': '{}',
   };
@@ -50,6 +50,7 @@ void main() {
     required Map<String, String> environment,
     ReleaseVersion? engineVersion,
     Map<String, String>? dimensions,
+    String? prefix,
     bool verbose = false,
     io.ProcessResult Function(List<String> command) onRun = _runUnhandled,
   }) {
@@ -62,6 +63,7 @@ void main() {
       verbose: verbose,
       stderr: fixture.outputSink,
       environment: environment,
+      prefix: prefix,
     );
   }
 
@@ -306,6 +308,51 @@ void main() {
     }
   });
 
+  test('addImg uses prefix, if specified', () async {
+    final _TestFixture fixture = _TestFixture();
+    try {
+      final SkiaGoldClient client = createClient(
+        fixture,
+        environment: presubmitEnv,
+        prefix: 'engine.',
+        onRun: (List<String> command) {
+          if (command case ['git', ...]) {
+            return io.ProcessResult(0, 0, mockCommitHash, '');
+          }
+          if (command case ['python tools/goldctl.py', 'imgtest', 'init', ...]) {
+            return io.ProcessResult(0, 0, '', '');
+          }
+          expect(command, <String>[
+            'python tools/goldctl.py',
+            'imgtest',
+            'add',
+            '--work-dir',
+            p.join(fixture.workDirectory.path, 'temp'),
+            '--test-name',
+            'engine.test-name',
+            '--png-file',
+            p.join(fixture.workDirectory.path, 'temp', 'golden.png'),
+            '--add-test-optional-key',
+            'image_matching_algorithm:fuzzy',
+            '--add-test-optional-key',
+            'fuzzy_max_different_pixels:10',
+            '--add-test-optional-key',
+            'fuzzy_pixel_delta_threshold:0',
+          ]);
+          return io.ProcessResult(0, 0, '', '');
+        },
+      );
+
+      await client.addImg(
+        'test-name.foo',
+        io.File(p.join(fixture.workDirectory.path, 'temp', 'golden.png')),
+        screenshotSize: 1000,
+      );
+    } finally {
+      fixture.dispose();
+    }
+  });
+
   test('addImg [pre-submit] executes successfully with a release version', () async {
     // Adds a suffix of "_Release_3_21" to the test name.
     final _TestFixture fixture = _TestFixture(
@@ -639,7 +686,7 @@ void main() {
 
       final String hash = client.getTraceID('test-name');
       fixture.httpClient.setJsonResponse(
-        Uri.parse('https://flutter-engine-gold.skia.org/json/v2/latestpositivedigest/$hash'),
+        Uri.parse('https://flutter-gold.skia.org/json/v2/latestpositivedigest/$hash'),
         <String, Object?>{'digest': 'digest'},
       );