GN + Android: allow to set visibility on android_library targets.

R=cjhopman@chromium.org
BUG=None

Review URL: https://codereview.chromium.org/755183004

Cr-Original-Commit-Position: refs/heads/master@{#305717}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 97ce2aed19d80cb905bdf7a165fd212fbdde54da

config/android/internal_rules.gni

@@ -814,6 +814,9 @@ template("java_library_impl") {
   }
 
   group(target_name) {
+    if (defined(invoker.visibility)) {
+      visibility = invoker.visibility
+    }
     deps = _final_deps
     datadeps = _final_datadeps
   }

config/android/rules.gni

@@ -848,6 +848,7 @@ template("android_library") {
     if (defined(invoker.srcjar_deps)) { srcjar_deps = invoker.srcjar_deps }
     if (defined(invoker.srcjars)) { srcjars = invoker.srcjars }
     if (defined(invoker.testonly)) { testonly = invoker.testonly }
+    if (defined(invoker.visibility)) { visibility = invoker.visibility }
     if (defined(invoker.dex_path)) { dex_path = invoker.dex_path }
 
     supports_android = true