Have fuchsia bin/run wrappers call test_env.py directly

Currently, when a bot runs a test (say, url_unittests) on Fuchsia,
it'll launch `python test_env.py bin/run_url_unittests` (roughly
speaking).

This CL flips that around so that the generated bin/run_ wrapper
script launches url_unittests (and the bot will invoke
bin/run_url_unittests directly).

This will make Fuchsia consistent with desktop, iOS, and LaCrOS;
ChromeOS and Android will be converted to match as well in
separate CLs.

Bug: 816629
Change-Id: Ic06adf43d9b80a1d454b5b691121dd76e22651e6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2360128
Reviewed-by: Sergey Ulanov <sergeyu@chromium.org>
Reviewed-by: Ben Pastene <bpastene@chromium.org>
Reviewed-by: Kevin Marshall <kmarshall@chromium.org>
Commit-Queue: Dirk Pranke <dpranke@google.com>
Cr-Commit-Position: refs/heads/master@{#821932}

build/config/fuchsia/generate_runner_scripts.gni

@@ -42,6 +42,8 @@ declare_args() {
 #       "build/fuchsia". Defaults to "test_runner.py".
 #   install_only: If true, executing the script will only install the package
 #       on the device, but not run it.
+#   is_test_exe: If true, the generated script will run the command under
+#       test_env.py and add arguments expected to be passed to test exes.
 template("fuchsia_package_runner") {
   forward_variables_from(invoker, [ "runner_script" ])
 
@@ -70,11 +72,29 @@ template("fuchsia_package_runner") {
                              "testonly",
                            ])
 
+    _is_test_exe = defined(invoker.is_test_exe) && invoker.is_test_exe
+
     if (defined(runner_script)) {
-      executable = rebase_path(runner_script)
+      _runner_script = runner_script
+    } else {
+      _runner_script = "//build/fuchsia/test_runner.py"
+    }
+
+    if (_is_test_exe) {
+      executable = "//testing/test_env.py"
+      executable_args =
+          [ "@WrappedPath(" + rebase_path(_runner_script, root_out_dir) + ")" ]
+      data = [
+        _runner_script,
+        "//.vpython",
+        "//testing/test_env.py",
+      ]
     } else {
-      executable = rebase_path("//build/fuchsia/test_runner.py")
+      executable = rebase_path(_runner_script)
+      executable_args = []
+      data = []
     }
+
     wrapper_script = generated_run_pkg_script_path
 
     data_deps = [
@@ -95,7 +115,7 @@ template("fuchsia_package_runner") {
 
     # Declares the files that are needed for test execution on the
     # swarming test client.
-    data = [
+    data += [
       "//build/fuchsia/",
       "//build/util/lib/",
       "//third_party/fuchsia-sdk/sdk/.build-id/",
@@ -142,8 +162,6 @@ template("fuchsia_package_runner") {
       data += [ "${fuchsia_additional_boot_image}/" ]
     }
 
-    executable_args = []
-
     package_paths = [ rebase_path(_package_path, root_build_dir) ]
     if (defined(invoker.package_deps)) {
       foreach(package_dep, invoker.package_deps) {

testing/test.gni

@@ -231,6 +231,7 @@ template("test") {
 
     fuchsia_package_runner(target_name) {
       testonly = true
+      is_test_exe = true
       forward_variables_from(invoker,
                              [
                                "use_test_server",

tools/mb/mb.py

@@ -1541,7 +1541,6 @@ def GetSwarmingCommand(self, target, vals):
         cmdline += ['--coverage-dir', '${ISOLATED_OUTDIR}']
     elif is_fuchsia and test_type != 'script':
       cmdline += [
-          '../../testing/test_env.py',
           os.path.join('bin', 'run_%s' % target),
           '--test-launcher-bot-mode',
           '--system-log-file', '${ISOLATED_OUTDIR}/system_log'