Reland "Lacros: create lacros tast test targets"

This is a reland of e2f3b551

Original change's description:
> Lacros: create lacros tast test targets
>
> This CL creates gn targets for lacros tast tests, and the main
> motivation is to run lacros tast tests on Chromium CI.
>
> Bug: 1158590
> Change-Id: I783779c3386a39743b8227367189b0b87832b9dc
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2606188
> Commit-Queue: Yuke Liao <liaoyuke@chromium.org>
> Reviewed-by: Ben Pastene <bpastene@chromium.org>
> Reviewed-by: Dirk Pranke <dpranke@google.com>
> Cr-Commit-Position: refs/heads/master@{#844127}

Bug: 1158590
Change-Id: I4baefe78970cb928476166875b519738be0c9f79
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2633073
Commit-Queue: Yuke Liao <liaoyuke@chromium.org>
Reviewed-by: Dirk Pranke <dpranke@google.com>
Reviewed-by: Ben Pastene <bpastene@chromium.org>
Cr-Commit-Position: refs/heads/master@{#844818}

chromeos/lacros/BUILD.gn

@@ -2,6 +2,7 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+import("//build/config/chromeos/rules.gni")
 import("//build/config/chromeos/ui_mode.gni")
 import("//build/config/linux/gtk/gtk.gni")
 import("//build/lacros/lacros_resource_sizes.gni")
@@ -30,3 +31,45 @@ component("lacros") {
 lacros_resource_sizes_test("resource_sizes_lacros_chrome") {
   data_deps = [ "//chrome:chrome" ]
 }
+
+# "cros_board" set in the GN args defines the board used to build lacros-chrome,
+# while the "override_board" here defines the board on which to test the built
+# binary, for more details, please refer to the "generate_runner_script"
+# template in //build/config/chromeos/rules.gni.
+template("lacros_tast_test_helper") {
+  forward_variables_from(invoker, [ "override_board" ])
+  assert(defined(override_board), "override_board is required")
+  lacros_tast_test(target_name) {
+    # TODO(crbug.com/1158590): use --attr-expr instead of hard-coding the tests.
+    tast_tests = [
+      "lacros.AudioPlay",
+      "lacros.AppLauncherLaunch",
+      "lacros.Basic",
+      "lacros.ShelfLaunch",
+    ]
+  }
+}
+
+# On Chromium CI, only a very limited number of boards are supported:
+# amd64-generic, eve, kevin etc, so just hard-coding them for simplicity.
+if (is_chromeos_device) {
+  _boards = [ cros_board ] + string_split(cros_boards, ":") +
+            string_split(cros_boards_with_qemu_images, ":")
+  foreach(b1,
+          [
+            "amd64-generic",
+            "eve",
+          ]) {
+    # To avoid duplicate definition of the targets.
+    matched = false
+    foreach(b2, _boards) {
+      if (!matched && b1 == b2) {
+        b1_underscore = string_replace(b1, "-", "_")
+        lacros_tast_test_helper("lacros_tast_tests_${b1_underscore}") {
+          override_board = b1
+        }
+        matched = true
+      }
+    }
+  }
+}