Remove many-many SpdyMajorVersion and NextProto arguments and members.

Now that SPDY/3.1 is disabled, rip it out from more areas of the code:

Remove SpdyMajorVersion and NextProto members, accessors, and function arguments
from BufferedSpdyFramer, SpdySession, SpdySessionPool, HeaderCoalescer,
SpdyStream classes, from spdy_http_utils.{h,cc}, and from flipserver.

Also deprecate Net.SpdySettingsCwndSent and Net.SpdyVersion3 histograms.

BUG=624095

Review-Url: https://codereview.chromium.org/2141993002
Cr-Commit-Position: refs/heads/master@{#405481}
43 files changed