On a 64-bit device when multiprocess is enabled:

1) if WebView is implemented by Monochrome, renderer processes are 32-bit, because monochrome's APK specifies that it prefers to be run in 32-bit mode to reduce Chrome memory usage.

2) if WebView is implemented by the standalone APK, renderer processes are 64-bit, because the flag isn't set in the webview APK.

This means that we'll get different memory usage, performance, startup time and bugs in multiprocess mode depending on which implementation is being used, even if they're the exact same version. This probably isn't desirable - we should add the prefer 32-bit flag to the WebView APKs as well, since one of the benefits of multiprocess is the ability to run the renderer in 32-bit to save memory even when webview is being used by a 64-bit app.