OS: Android

What steps will reproduce the problem?
(1) Build libchrome.so with is_official_build=true
(2) Dump symbols with nm
(3) Observe there are some that end with ForTesting


We shouldn't be shipping ForTesting code. The code is being kept because of the JNI boundary. Here's the list of them:
https://cs.chromium.org/search/?q=Java_.*Testing+file:cc&sq=package:chromium&type=cs
https://cs.chromium.org/search/?q=file:java+native.*ForTesting&sq=package:chromium&type=cs

Proposed solution:
1. Teach jni generator to guard symbols that end with "ForTesting" behind #ifdef OFFICIAL_BUILD
2. Add a new flag to resource_sizes.py: --assert-no-test-symbols