Place the mojo_android_application output at the root output directory.

This patch changes the mojo_android_application rule so that the
resulting .mojo file is placed at the root output directory, matching
the mojo_native_application rule.

R=qsr@chromium.org

Review URL: https://codereview.chromium.org/794603002
diff --git a/mojo/public/mojo_application.gni b/mojo/public/mojo_application.gni
index d28cb44..6f738bd 100644
--- a/mojo/public/mojo_application.gni
+++ b/mojo/public/mojo_application.gni
@@ -170,9 +170,9 @@
     }
 
     if (defined(invoker.output_name)) {
-      mojo_output = "$target_out_dir/" + invoker.output_name + ".mojo"
+      mojo_output = "$root_out_dir/" + invoker.output_name + ".mojo"
     } else {
-      mojo_output = "$target_out_dir/" + target_name + ".mojo"
+      mojo_output = "$root_out_dir/" + target_name + ".mojo"
     }
 
     action(target_name) {