make ChromiumDevice.stopApp a no-op if it has already been called (#156778)

(Hopefully) fixes https://github.com/flutter/flutter/issues/156700

To summarize that thread, there are a few ways to trigger cleanup logic
in `flutter run -d chrome`. For example, pressing `q` will close Chrome,
but Chrome closing triggers cleanup logic in the resident runner (which
includes trying to close Chrome, which is redundant).

A simple way to fix this is to not call `Chrome.close` in
`ChromiumDevice.stopApp` when we've already called it once. This
solution isn't ideal—consider a scenario where two calls to `stopApp`
are made concurrently. The second one would probably complete before the
browser is actually closed. However, I don't foresee anything ever
depending on `stopApp` finishing implying that the browser is closed.

I feel like there might be a yak to shave here (`ResidentWebRunner`
could keep track of its state and not initiate redundant cleanup
operations), but I am not sure its worth the continued effort.

<details>

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we expect every widget to implement].
- [x] I signed the [CLA].
- [x] I listed at least one issue that this PR fixes in the description
above.
- [x] I updated/added relevant documentation (doc comments with `///`).
- [x] I added new tests to check the change I am making, or this PR is
[test-exempt].
- [x] I followed the [breaking change policy] and added [Data Driven
Fixes] where supported.
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packages/flutter_tools/lib/src/web/web_device.dart

@@ -160,7 +160,9 @@ abstract class ChromiumDevice extends Device {
     ApplicationPackage? app, {
     String? userIdentifier,
   }) async {
-    await _chrome?.close();
+    final Future<void>? future = _chrome?.close();
+    _chrome = null;
+    await future;
     return true;
   }
 

packages/flutter_tools/test/general.shard/web/devices_test.dart

@@ -12,6 +12,7 @@ import 'package:flutter_tools/src/build_info.dart';
 import 'package:flutter_tools/src/device.dart';
 import 'package:flutter_tools/src/web/chrome.dart';
 import 'package:flutter_tools/src/web/web_device.dart';
+import 'package:test/fake.dart';
 
 import '../../src/common.dart';
 import '../../src/fake_process_manager.dart';
@@ -32,6 +33,29 @@ void main() {
     expect(await webDevices.pollingGetDevices(), isEmpty);
   });
 
+  testWithoutContext('Successive calls of ChromiumDevice.stopApp() do not try to close chrome', () async {
+    final TestChromiumLauncher launcher = TestChromiumLauncher(
+      launcher: () => _OnceClosableChromium(),
+    );
+
+    final _FakeChromiumDevice chromiumDevice = _FakeChromiumDevice(
+      chromiumLauncher: launcher,
+      fileSystem: MemoryFileSystem.test(),
+      logger: BufferLogger.test(),
+    );
+
+    await chromiumDevice.startApp(
+      null,
+      debuggingOptions: DebuggingOptions.enabled(BuildInfo.debug),
+      platformArgs: <String, Object?>{
+        'uri': '/',
+      }
+    );
+
+    await chromiumDevice.stopApp(null);
+    await chromiumDevice.stopApp(null);
+  });
+
   testWithoutContext('GoogleChromeDevice defaults', () async {
     final TestChromiumLauncher launcher = TestChromiumLauncher();
 
@@ -392,7 +416,11 @@ void main() {
 
 /// A test implementation of the [ChromiumLauncher] that launches a fixed instance.
 class TestChromiumLauncher implements ChromiumLauncher {
-  TestChromiumLauncher();
+  TestChromiumLauncher({Chromium Function()? launcher}) {
+    _launcher = launcher ?? () => _UnimplementedChromium();
+  }
+
+  late Chromium Function() _launcher;
 
   @override
   Completer<Chromium> currentCompleter = Completer<Chromium>();
@@ -422,6 +450,7 @@ class TestChromiumLauncher implements ChromiumLauncher {
     Directory? cacheDir,
     List<String> webBrowserFlags = const <String>[],
   }) async {
+    currentCompleter.complete(_launcher());
     return currentCompleter.future;
   }
 
@@ -430,3 +459,34 @@ class TestChromiumLauncher implements ChromiumLauncher {
     return currentCompleter.future;
   }
 }
+
+class _FakeChromiumDevice extends ChromiumDevice {
+  _FakeChromiumDevice(
+      {required ChromiumLauncher chromiumLauncher,
+      required super.fileSystem,
+      required super.logger})
+      : super(
+          name: 'fake name',
+          chromeLauncher: chromiumLauncher,
+        );
+
+  @override
+  Future<String> get sdkNameAndVersion async => 'fake sdkNameAndVersion';
+
+  @override
+  String get name => 'fake name';
+}
+
+class _OnceClosableChromium extends Fake implements Chromium {
+  bool _closed = false;
+
+  @override
+  Future<void> close() async {
+    if (_closed) {
+      throw Exception('Already closed');
+    }
+    _closed = true;
+  }
+}
+
+class _UnimplementedChromium extends Fake implements Chromium { }