Add flutter startup benchmark

As directed on
flutter#111461 (comment)

.ci.yaml

@@ -4441,3 +4441,33 @@ targets:
       tags: >
         ["devicelab", "hostonly"]
       task_name: windows_startup_test
+
+  - name: Windows flutter_tool_startup
+    bringup: true
+    recipe: devicelab/devicelab_drone
+    presubmit: false
+    timeout: 60
+    properties:
+      tags: >
+        ["devicelab", "hostonly"]
+      task_name: flutter_tool_startup__windows
+
+  - name: Linux flutter_tool_startup
+    bringup: true
+    recipe: devicelab/devicelab_drone
+    presubmit: false
+    timeout: 60
+    properties:
+      tags: >
+        ["devicelab", "hostonly"]
+      task_name: flutter_tool_startup__linux
+
+  - name: Mac flutter_tool_startup
+    bringup: true
+    recipe: devicelab/devicelab_drone
+    presubmit: false
+    timeout: 60
+    properties:
+      tags: >
+        ["devicelab", "hostonly"]
+      task_name: flutter_tool_startup__mac

TESTOWNERS

@@ -220,6 +220,9 @@
 /dev/devicelab/bin/tasks/flutter_gallery_win_desktop__compile.dart @yaakovschectman @flutter/desktop
 /dev/devicelab/bin/tasks/flutter_gallery_win_desktop__start_up.dart @yaakovschectman @flutter/desktop
 /dev/devicelab/bin/tasks/flutter_view_macos__start_up.dart @a-wallen @flutter/desktop
+/dev/devicelab/bin/tasks/flutter_tool_startup__windows.dart @jensj @flutter/tool
+/dev/devicelab/bin/tasks/flutter_tool_startup__linux.dart @jensj @flutter/tool
+/dev/devicelab/bin/tasks/flutter_tool_startup__macos.dart @jensj @flutter/tool
 /dev/devicelab/bin/tasks/flutter_view_win_desktop__start_up.dart @yaakovschectman @flutter/desktop
 /dev/devicelab/bin/tasks/gradle_desugar_classes_test.dart @zanderso @flutter/tool
 /dev/devicelab/bin/tasks/gradle_non_android_plugin_test.dart @stuartmorgan @flutter/plugin