[WebView] Only pass one path to relro creation/loading at a time.

There's no need to send both 32-bit and 64-bit paths to the native side
of the relro-creation/loading logic, we can check which one to send on
the java side instead.

Bug: 28736099
Test: Load WebView app, ensure relro file is loaded into the app
process.

Change-Id: Ia3fb4b3ed686c3e70c26a384aae966bda179d225