Disable SPDY pooling

Bug: 16799113

The original patch is
https://codereview.chromium.org/417013005
We only take the SPDY part since Quic is not enabled.

Change-Id: Ie25ab23b1984d1e87e6019df0224fe8d7f388828
(cherry picked from commit f7d8edb81309f040509b1cfd64f0a2d7827ade94)