Fix flakiness of commands_test (#11705)

- Wait for full Hot Reload
- Wait for full Restart
- Fallback if checkHealth throws METHOD_NOT_FOUND.
  We try to wait for the service extensions to be registered and retry.

dev/devicelab/bin/tasks/commands_test.dart

@@ -77,15 +77,21 @@ void main() {
       await driver.drive('none');
       final Future<String> reloadStartingText =
         stdout.stream.firstWhere((String line) => line.endsWith('hot reload...'));
+      final Future<String> reloadEndingText =
+        stdout.stream.firstWhere((String line) => line.contains('Hot reload performed in '));
       print('test: pressing "r" to perform a hot reload...');
       run.stdin.write('r');
       await reloadStartingText;
+      await reloadEndingText;
       await driver.drive('none');
       final Future<String> restartStartingText =
         stdout.stream.firstWhere((String line) => line.endsWith('full restart...'));
+      final Future<String> restartEndingText =
+        stdout.stream.firstWhere((String line) => line.contains('Restart performed in '));
       print('test: pressing "R" to perform a full reload...');
       run.stdin.write('R');
       await restartStartingText;
+      await restartEndingText;
       await driver.drive('none');
       run.stdin.write('q');
       final int result = await run.exitCode;

dev/devicelab/manifest.yaml

@@ -125,7 +125,6 @@ tasks:
       Runs tests of flutter run commands.
     stage: devicelab
     required_agent_capabilities: ["has-android-device"]
-    flaky: true
 
   android_sample_catalog_generator:
     description: >

packages/flutter_driver/lib/src/driver.dart

@@ -7,6 +7,7 @@ import 'dart:convert';
 import 'dart:io';
 
 import 'package:file/file.dart' as f;
+import 'package:json_rpc_2/error_code.dart' as error_code;
 import 'package:json_rpc_2/json_rpc_2.dart' as rpc;
 import 'package:meta/meta.dart';
 import 'package:path/path.dart' as p;
@@ -207,10 +208,6 @@ class FlutterDriver {
       });
     }
 
-    // Attempt to resume isolate if it was paused
-    if (isolate.pauseEvent is VMPauseStartEvent) {
-      _log.trace('Isolate is paused at start.');
-
     // Waits for a signal from the VM service that the extension is registered
     Future<String> waitForServiceExtension() {
       return isolate.onExtensionAdded.firstWhere((String extension) {
@@ -231,6 +228,10 @@ class FlutterDriver {
       });
     }
 
+    // Attempt to resume isolate if it was paused
+    if (isolate.pauseEvent is VMPauseStartEvent) {
+      _log.trace('Isolate is paused at start.');
+
       // If the isolate is paused at the start, e.g. via the --start-paused
       // option, then the VM service extension is not registered yet. Wait for
       // it to be registered.
@@ -269,8 +270,27 @@ class FlutterDriver {
       );
     }
 
+    // Invoked checkHealth and try to fix delays in the registration of Service
+    // extensions
+    Future<Health> checkHealth() async {
+      try {
         // At this point the service extension must be installed. Verify it.
-    final Health health = await driver.checkHealth();
+        return await driver.checkHealth();
+      } on rpc.RpcException catch (e) {
+        if (e.code != error_code.METHOD_NOT_FOUND) {
+          rethrow;
+        }
+        _log.trace(
+          'Check Health failed, try to wait for the service extensions to be'
+          'registered.'
+        );
+        await enableIsolateStreams();
+        await waitForServiceExtension().timeout(_kLongTimeout * 2);
+        return driver.checkHealth();
+      }
+    }
+
+    final Health health = await checkHealth();
     if (health.status != HealthStatus.ok) {
       await client.close();
       throw new DriverError('Flutter application health check failed.');