Create separate target for CastSysInfoAndroidThings for testing.

Bug: internal b/120633112
Test: Ran unit tests
Change-Id: Idbda6d8ff9b26db40b924dc1bf9d56ab331d4e8e
Reviewed-on: https://chromium-review.googlesource.com/c/1366389Reviewed-by: Simeon Anfinrud <sanfin@chromium.org>
Commit-Queue: Alex Leung <alexleung@google.com>
Cr-Commit-Position: refs/heads/master@{#615608}

chromecast/browser/android/BUILD.gn

@@ -158,14 +158,33 @@ android_library("cast_shell_java") {
   }
 
   if (is_android_things_non_public && !build_for_android_things_n) {
-    java_files += [ "$java_src_dir/org/chromium/chromecast/shell/CastSysInfoAndroidThings.java" ]
-    deps += [ "//chromecast/internal/android/prebuilt/things:support_lib_java" ]
+    deps += [ ":cast_shell_android_things_sys_info_java" ]
     if (enable_assistant) {
       deps += [ "//chromecast/internal/assistant/ui:boot_parameters_java" ]
     }
   }
 }
 
+if (is_android_things_non_public && !build_for_android_things_n) {
+  android_library("cast_shell_android_things_sys_info_java") {
+    java_files = [ "//chromecast/browser/android/apk/src/org/chromium/chromecast/shell/CastSysInfoAndroidThings.java" ]
+    deps = [
+      "//base:base_java",
+      "//chromecast/internal/android/prebuilt/things:support_lib_java",
+    ]
+  }
+
+  generate_jni("cast_shell_android_things_sys_info_jni_headers") {
+    sources = [
+      "//chromecast/browser/android/apk/src/org/chromium/chromecast/shell/CastSysInfoAndroidThings.java",
+    ]
+    deps = [
+      "//chromecast/internal/android/prebuilt/things:support_lib_java",
+    ]
+    jni_package = "chromecast"
+  }
+}
+
 junit_binary("cast_shell_junit_tests") {
   java_files = [
     "junit/src/org/chromium/chromecast/shell/AsyncTaskRunnerTest.java",