[ci] Drive tests with html renderer if CHANNEL is stable. (#7146)

Introduces a small fork in the `drive_examples_command` to run integration tests with `--web-renderer=html` in the `stable` channel (and `--web-renderer=canvaskit` in `master`).

This is supposed to be removed, once the current `master` rolls into `stable` (see clean-up issue referenced below).

## Issues

* Part of: flutter/flutter#143543
* Prevents flakes: #7115 (comment)
* Clean-up issue: flutter/flutter#151869

Author: ditman

script/tool/lib/src/drive_examples_command.dart

@@ -119,7 +119,11 @@ class DriveExamplesCommand extends PackageLoopingCommand {
           'web-server',
           '--web-port=7357',
           '--browser-name=chrome',
-          '--web-renderer=canvaskit',
+          // TODO(dit): Clean this up, https://github.com/flutter/flutter/issues/151869
+          if (platform.environment['CHANNEL']?.toLowerCase() == 'master')
+            '--web-renderer=canvaskit',
+          if (platform.environment['CHANNEL']?.toLowerCase() != 'master')
+            '--web-renderer=html',
           if (platform.environment.containsKey('CHROME_EXECUTABLE'))
             '--chrome-binary=${platform.environment['CHROME_EXECUTABLE']}',
         ],

script/tool/test/drive_examples_command_test.dart

@@ -38,6 +38,9 @@ void main() {
       runner = CommandRunner<void>(
           'drive_examples_command', 'Test for drive_example_command');
       runner.addCommand(command);
+
+      // TODO(dit): Clean this up, https://github.com/flutter/flutter/issues/151869
+      mockPlatform.environment['CHANNEL'] = 'master';
     });
 
     void setMockFlutterDevicesOutput({
@@ -688,6 +691,60 @@ void main() {
           ]));
     });
 
+    // TODO(dit): Clean this up, https://github.com/flutter/flutter/issues/151869
+    test('drives a web plugin (html renderer in stable)', () async {
+      // Override the platform to simulate CHANNEL: stable
+      mockPlatform.environment['CHANNEL'] = 'stable';
+
+      final RepositoryPackage plugin = createFakePlugin(
+        'plugin',
+        packagesDir,
+        extraFiles: <String>[
+          'example/integration_test/plugin_test.dart',
+          'example/test_driver/integration_test.dart',
+          'example/web/index.html',
+        ],
+        platformSupport: <String, PlatformDetails>{
+          platformWeb: const PlatformDetails(PlatformSupport.inline),
+        },
+      );
+
+      final Directory pluginExampleDirectory = getExampleDir(plugin);
+
+      final List<String> output = await runCapturingPrint(runner, <String>[
+        'drive-examples',
+        '--web',
+      ]);
+
+      expect(
+        output,
+        containsAllInOrder(<Matcher>[
+          contains('Running for plugin'),
+          contains('No issues found!'),
+        ]),
+      );
+
+      expect(
+          processRunner.recordedCalls,
+          orderedEquals(<ProcessCall>[
+            ProcessCall(
+                getFlutterCommand(mockPlatform),
+                const <String>[
+                  'drive',
+                  '-d',
+                  'web-server',
+                  '--web-port=7357',
+                  '--browser-name=chrome',
+                  '--web-renderer=html',
+                  '--driver',
+                  'test_driver/integration_test.dart',
+                  '--target',
+                  'integration_test/plugin_test.dart',
+                ],
+                pluginExampleDirectory.path),
+          ]));
+    });
+
     test('runs chromedriver when requested', () async {
       final RepositoryPackage plugin = createFakePlugin(
         'plugin',