Add GN for sandbox_linux_jni_unittests

BUG=

Review URL: https://codereview.chromium.org/936163003

Cr-Commit-Position: refs/heads/master@{#317445}

sandbox/linux/BUILD.gn

@@ -63,8 +63,10 @@ source_set("sandbox_linux_test_utils") {
   }
 }
 
-# The main sandboxing test target.
-test("sandbox_linux_unittests") {
+# Sources shared by sandbox_linux_unittests and sandbox_linux_jni_unittests.
+source_set("sandbox_linux_unittests_sources") {
+  testonly = true
+
   sources = [
     "services/proc_util_unittest.cc",
     "services/resource_limits_unittests.cc",
@@ -127,23 +129,24 @@ test("sandbox_linux_unittests") {
   }
 }
 
-# TODO(GYP) Android version of this test.
-#    {
-#      # This target is the shared library used by Android APK (i.e.
-#      # JNI-friendly) tests.
-#      "target_name": "sandbox_linux_jni_unittests",
-#      "includes": [
-#        "sandbox_linux_test_sources.gypi",
-#      ],
-#      "type": "shared_library",
-#      "conditions": [
-#        [ "OS == "android"", {
-#          "dependencies": [
-#            "../testing/android/native_test.gyp:native_test_native_code",
-#          ],
-#        }],
-#      ],
-#    },
+# The main sandboxing test target.
+test("sandbox_linux_unittests") {
+  deps = [
+    ":sandbox_linux_unittests_sources",
+  ]
+}
+
+# This target is the shared library used by Android APK (i.e.
+# JNI-friendly) tests.
+shared_library("sandbox_linux_jni_unittests") {
+  testonly = true
+  deps = [
+    ":sandbox_linux_unittests_sources",
+  ]
+  if (is_android) {
+    deps += [ "//testing/android:native_test_native_code" ]
+  }
+}
 
 component("seccomp_bpf") {
   sources = [