Undeprecate CronetEngine.Builder#enableLegacyMode

Undeprecate CronetEngine.Builder#enableLegacyMode

This CL undeprecate CronetEngine.Builder#enableLegacyMode because legacy mode
is now supported by JavaCronetEngine.

R=mef@chromium.org

[xunjieli, 2016-08-31 17:16:33]

Description was changed from

==========
Undeprecate CronetEngine.Builder#enableLegacyMode

This CL undeprecate CronetEngine.Builder#enableLegacyMode because legacy mode
is now supported by JavaCronetEngine.

R=mef@chromium.org
==========

to

==========
Undeprecate CronetEngine.Builder#enableLegacyMode

This CL undeprecate CronetEngine.Builder#enableLegacyMode because legacy mode
is now supported by JavaCronetEngine.

R=mef@chromium.org
==========

[xunjieli, 2016-08-31 17:19:14]

+kapishnikov@
Andrei and Miriam mentioned that the enableLegacyMode() name might not be clear
as to what it actually does, and maybe we should rename it in this CL. We can do
useJavaImplementationOnly() or disableNativeImplementation(). Happy to take any
other suggestions as well. What do you think?

[pauljensen, 2016-09-06 12:01:37]

I think the name definitely has to change, but I think we also need a massive
comment because this very drastically changes the behavior of Cronet (e.g. no
QUIC, no HTTP2, no NQE, no UMA, no cert pinning etc) and it does so in the most
dangerous way: silently ignoring calls to enable these options.  We also might
want to change this function to take an enum that allows for disabling Java-only
fallback, so as to address http://crbug.com/600690

[xunjieli, 2016-09-06 13:04:23]

On 2016/09/06 12:01:37, pauljensen wrote:
> I think the name definitely has to change, but I think we also need a massive
> comment because this very drastically changes the behavior of Cronet (e.g. no
> QUIC, no HTTP2, no NQE, no UMA, no cert pinning etc) and it does so in the
most
> dangerous way: silently ignoring calls to enable these options.  We also might
> want to change this function to take an enum that allows for disabling
Java-only
> fallback, so as to address http://crbug.com/600690

Thanks everyone for the suggestions! I filed crbug.com/644247 to track this. I
will close this in the meanwhile.