Revert of Revert "net: enable SSL_MODE_CBC_RECORD_SPLITTING with OpenSSL."...

Revert of Revert "net: enable SSL_MODE_CBC_RECORD_SPLITTING with OpenSSL." (patchset #1 id:1 of https://codereview.chromium.org/547843002/)

Reason for revert:
Doesn't look like this helped with the perf regression, so undoing the original revert.

Original issue's description:
> Revert "net: enable SSL_MODE_CBC_RECORD_SPLITTING with OpenSSL."
>
> This reverts commit e06bd133.
>
> This is a preemptive revert to see whether a pagecycler regression can
> be attributed to this change. (Even if it can, we still probably want to
> make the change, but it's good to know.)
>
> BUG=409214
> TBR=davidben@chromium.org
>
> Committed: https://chromium.googlesource.com/chromium/src/+/5fee53e7fe9a5a0f6aeb568446d8cdee5e3a96b7

TBR=davidben@chromium.org,agl@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=409214

Review URL: https://codereview.chromium.org/559663003

Cr-Commit-Position: refs/heads/master@{#294001}

net/socket/ssl_client_socket_openssl.cc

@@ -752,6 +752,7 @@ int SSLClientSocketOpenSSL::Init() {
   SslSetClearMask mode;
 
   mode.ConfigureFlag(SSL_MODE_RELEASE_BUFFERS, true);
+  mode.ConfigureFlag(SSL_MODE_CBC_RECORD_SPLITTING, true);
 
   mode.ConfigureFlag(SSL_MODE_HANDSHAKE_CUTTHROUGH,
                      ssl_config_.false_start_enabled);