Fix: use --web-launch-url and --web-hostname arguments in flutter drive (#131763)

Implement expected functionalities when supplying `--web-launch-url` and/or `--web-hostname` arguments to `flutter drive`.
- `--web-launch-url` now sets the starting url for the (headless) browser
  - Which for example means you can start at a certain part of the app at the start of your integration test
- `--web-hostname` now sets the hostname where the target of flutter drive will be hosted
  - Which allows you to set something other than localhost (allowing access via a reverse-proxy for example)

Fixes #118028

dev/integration_tests/flutter_gallery/.gitignore

@@ -1,3 +1,2 @@
-lib/generated_plugin_registrant.dart
 vmservice.out
 *.sksl.json

packages/flutter_tools/lib/src/drive/web_driver_service.dart

@@ -41,6 +41,9 @@ class WebDriverService extends DriverService {
   late ResidentRunner _residentRunner;
   Uri? _webUri;
 
+  @visibleForTesting
+  Uri? get webUri => _webUri;
+
   /// The result of [ResidentRunner.run].
   ///
   /// This is expected to stay `null` throughout the test, as the application
@@ -74,10 +77,12 @@ class WebDriverService extends DriverService {
         DebuggingOptions.disabled(
           buildInfo,
           port: debuggingOptions.port,
+          hostname: debuggingOptions.hostname,
         )
         : DebuggingOptions.enabled(
           buildInfo,
           port: debuggingOptions.port,
+          hostname: debuggingOptions.hostname,
           disablePortPublication: debuggingOptions.disablePortPublication,
         ),
       stayResident: true,
@@ -116,11 +121,16 @@ class WebDriverService extends DriverService {
       throw ToolExit('Failed to start application');
     }
 
-    _webUri = _residentRunner.uri;
+    if (_residentRunner.uri == null) {
-
-    if (_webUri == null) {
       throw ToolExit('Unable to connect to the app. URL not available.');
     }
+
+    if (debuggingOptions.webLaunchUrl != null) {
+      // It should thow an error if the provided url is invalid so no tryParse
+      _webUri = Uri.parse(debuggingOptions.webLaunchUrl!);
+    } else {
+      _webUri = _residentRunner.uri;
+    }
   }
 
   @override

packages/flutter_tools/test/general.shard/drive/web_driver_service_test.dart

@@ -258,6 +258,29 @@ void main() {
     WebRunnerFactory: () => FakeWebRunnerFactory(),
   });
 
+  testUsingContext('WebDriverService can start an app with a launch url provided', () async {
+    final WebDriverService service = setUpDriverService();
+    final FakeDevice device = FakeDevice();
+    const String testUrl = 'http://localhost:1234/test';
+    await service.start(BuildInfo.profile, device, DebuggingOptions.enabled(BuildInfo.profile, webLaunchUrl: testUrl), true);
+    await service.stop();
+    expect(service.webUri, Uri.parse(testUrl));
+  }, overrides: <Type, Generator>{
+    WebRunnerFactory: () => FakeWebRunnerFactory(),
+  });
+
+  testUsingContext('WebDriverService will throw when an invalid launch url is provided', () async {
+    final WebDriverService service = setUpDriverService();
+    final FakeDevice device = FakeDevice();
+    const String invalidTestUrl = '::INVALID_URL::';
+    await expectLater(
+      service.start(BuildInfo.profile, device, DebuggingOptions.enabled(BuildInfo.profile, webLaunchUrl: invalidTestUrl), true),
+      throwsA(isA<FormatException>()),
+    );
+  }, overrides: <Type, Generator>{
+    WebRunnerFactory: () => FakeWebRunnerFactory(),
+  });
+
   testUsingContext('WebDriverService forwards exception when run future fails before app starts', () async {
     final WebDriverService service = setUpDriverService();
     final Device device = FakeDevice();