Changing SpawnChild to return a struct.

base/test/BUILD.gn

Index: base/test/BUILD.gn
diff --git a/base/test/BUILD.gn b/base/test/BUILD.gn
index 844707ebd190948d993e5e62f2747516aaa4fa93..68d9f130ef790c80101aaabe3332a8e67a35060a 100644
--- a/base/test/BUILD.gn
+++ b/base/test/BUILD.gn
@@ -28,6 +28,8 @@ static_library("test_support") {
     "../trace_event/trace_config_memory_test_util.h",
     "android/java_handler_thread_for_testing.cc",
     "android/java_handler_thread_for_testing.h",
+    "android/jni_test_util.cc",
+    "android/jni_test_util.h",
     "android/test_system_message_handler_link_android.cc",
     "android/test_system_message_handler_link_android.h",
     "fuzzed_data_provider.cc",
@@ -337,6 +339,7 @@ if (is_android) {
 
   generate_jni("test_support_jni_headers") {
     sources = [
+      "android/java/src/org/chromium/base/LaunchClientResult.java",
       "android/java/src/org/chromium/base/MainReturnCodeResult.java",
       "android/java/src/org/chromium/base/MultiprocessTestClientLauncher.java",
     ]
@@ -347,6 +350,7 @@ if (is_android) {
     testonly = true
     deps = [
       "//base:base_java",
+      "//mojo/public/java:system_java",
       "//testing/android/native_test:native_main_runner_java",
       "//third_party/android_tools:android_support_annotations_java",
       "//third_party/jsr-305:jsr_305_javalib",
@@ -354,6 +358,7 @@ if (is_android) {
     srcjar_deps = [ ":test_support_java_aidl" ]
     java_files = [
       "android/java/src/org/chromium/base/FileDescriptorInfo.java",
+      "android/java/src/org/chromium/base/LaunchClientResult.java",
       "android/java/src/org/chromium/base/MainReturnCodeResult.java",
       "android/java/src/org/chromium/base/MultiprocessTestClientLauncher.java",
       "android/java/src/org/chromium/base/MultiprocessTestClientService.java",