Minor fixes to junit and robolectric BUILD.gn files.

testing/android/junit/BUILD.gn

Index: testing/android/junit/BUILD.gn
diff --git a/testing/android/junit/BUILD.gn b/testing/android/junit/BUILD.gn
index f80d0b57377e5acef0e05f14ec981328c4285f5c..a338fca3e586185682a5e7786b1f70b3ac6a6f8a 100644
--- a/testing/android/junit/BUILD.gn
+++ b/testing/android/junit/BUILD.gn
@@ -8,6 +8,7 @@ import("//build/config/android/rules.gni")
 
 # GYP: //testing/android/junit_test.gyp:junit_test_support
 java_library("junit_test_support") {
+  testonly = true
   DEPRECATED_java_in_dir = "java/src"
   deps = [
     "//third_party/junit",
@@ -18,6 +19,7 @@ java_library("junit_test_support") {
 
 # GYP: //testing/android/junit_test.gyp:junit_unit_tests
 java_binary("junit_unittests") {
+  testonly = true
   deps = [
     ":junit_test_support",
     "//third_party/junit",