kill leaked chrome processes (#39514)

dev/devicelab/lib/framework/running_processes.dart

@@ -14,7 +14,7 @@ class RunningProcessInfo {
         assert(commandLine != null);
 
   final String commandLine;
-  final int pid;
+  final String pid;
   final DateTime creationDate;
 
   @override
@@ -47,7 +47,7 @@ class RunningProcessInfo {
   }
 }
 
-Future<bool> killProcess(int pid, {ProcessManager processManager}) async {
+Future<bool> killProcess(String pid, {ProcessManager processManager}) async {
   assert(pid != null, 'Must specify a pid to kill');
   processManager ??= const LocalProcessManager();
   ProcessResult result;
@@ -55,14 +55,14 @@ Future<bool> killProcess(int pid, {ProcessManager processManager}) async {
     result = await processManager.run(<String>[
       'taskkill.exe',
       '/pid',
-      pid.toString(),
+      pid,
       '/f',
     ]);
   } else {
     result = await processManager.run(<String>[
       'kill',
       '-9',
-      pid.toString(),
+      pid,
     ]);
   }
   return result.exitCode == 0;
@@ -163,7 +163,7 @@ Iterable<RunningProcessInfo> processPowershellOutput(String output) sync* {
       time = '${hours + 12}${time.substring(2)}';
     }
 
-    final int pid = int.parse(line.substring(0, processIdHeaderSize).trim());
+    final String pid = line.substring(0, processIdHeaderSize).trim();
     final DateTime creationDate = DateTime.parse('$year-$month-${day}T$time');
     final String commandLine = line.substring(commandLineHeaderStart).trim();
     yield RunningProcessInfo(pid, creationDate, commandLine);
@@ -254,7 +254,7 @@ Iterable<RunningProcessInfo> processPsOutput(
     final DateTime creationDate = DateTime.parse('$year-$month-${day}T$time');
     line = line.substring(24).trim();
     final int nextSpace = line.indexOf(' ');
-    final int pid = int.parse(line.substring(0, nextSpace));
+    final String pid = line.substring(0, nextSpace);
     final String commandLine = line.substring(nextSpace + 1);
     yield RunningProcessInfo(pid, creationDate, commandLine);
   }

dev/devicelab/lib/tasks/web_dev_mode_tests.dart

@@ -9,6 +9,7 @@ import 'dart:io';
 import 'package:path/path.dart' as path;
 
 import '../framework/framework.dart';
+import '../framework/running_processes.dart';
 import '../framework/utils.dart';
 
 final Directory _editedFlutterGalleryDir = dir(path.join(Directory.systemTemp.path, 'edited_flutter_gallery'));
@@ -20,6 +21,18 @@ TaskFunction createWebDevModeTest() {
       '--hot', '-d', 'chrome', '--verbose', '--resident', '--target=lib/main.dart',
     ];
     int hotRestartCount = 0;
+    String chromeProcessName;
+    if (Platform.isMacOS) {
+      chromeProcessName = 'Chrome';
+    } else if (Platform.isLinux) {
+      chromeProcessName = 'chrome';
+    } else if (Platform.isWindows) {
+      chromeProcessName = 'chrome.exe';
+    }
+    final Set<String> beforeChromeProcesses = await getRunningProcesses(processName: chromeProcessName)
+      .map((RunningProcessInfo info) => info.pid)
+      .toSet();
+    try {
       await inDirectory<void>(flutterDirectory, () async {
         rmTree(_editedFlutterGalleryDir);
         mkdirs(_editedFlutterGalleryDir);
@@ -133,6 +146,15 @@ TaskFunction createWebDevModeTest() {
           }
         });
       });
+    } finally {
+      final Set<String> afterChromeProcesses = await getRunningProcesses(processName: chromeProcessName)
+        .map((RunningProcessInfo info) => info.pid)
+        .toSet();
+      final Set<String> newProcesses = afterChromeProcesses.difference(beforeChromeProcesses);
+      for (String processId in newProcesses) {
+        await killProcess(processId);
+      }
+    }
     if (hotRestartCount != 1) {
       return TaskResult.failure(null);
     }

dev/devicelab/test/running_processes_test.dart

@@ -24,17 +24,17 @@ ProcessId CreationDate         CommandLine
         results,
         equals(<RunningProcessInfo>[
           RunningProcessInfo(
-            6552,
+            '6552',
             DateTime(2019, 7, 3, 17, 0, 27),
             r'"C:\tools\dart-sdk\bin\dart.exe" .\bin\agent.dart ci',
           ),
           RunningProcessInfo(
-            6553,
+            '6553',
             DateTime(2019, 7, 3, 22, 0, 27),
             r'"C:\tools\dart-sdk1\bin\dart.exe" .\bin\agent.dart ci',
           ),
           RunningProcessInfo(
-            6554,
+            '6554',
             DateTime(2019, 7, 3, 11, 0, 27),
             r'"C:\tools\dart-sdk2\bin\dart.exe" .\bin\agent.dart ci',
           ),
@@ -54,12 +54,12 @@ Sat Mar  9 20:13:00 2019        49 /usr/sbin/syslogd
         results,
         equals(<RunningProcessInfo>[
           RunningProcessInfo(
-            1,
+            '1',
             DateTime(2019, 3, 9, 20, 12, 47),
             '/sbin/launchd',
           ),
           RunningProcessInfo(
-            49,
+            '49',
             DateTime(2019, 3, 9, 20, 13, 00),
             '/usr/sbin/syslogd',
           ),