jni_generator: Use shortened name for GEN_JNI when !is_java_debug

To save space in release, instead of using org.chromium.base.natives.GEN_JNI
use a short package/class name, J.N. Proguard won't do this for us because
we can't obfuscate any class that contains native methods.

Bug: 898261
Change-Id: I84ad6914912b5b0e0d390d53a88dbcf41633edbf
Reviewed-on: https://chromium-review.googlesource.com/c/1347034
Reviewed-by: agrieve <agrieve@chromium.org>
Reviewed-by: Eric Stevenson <estevenson@chromium.org>
Commit-Queue: agrieve <agrieve@chromium.org>
Cr-Commit-Position: refs/heads/master@{#610288}
6 files changed