Make HttpNetworkSession::host_mapping_rules no longer a pointer.

TBR=dimich@chromium.org
BUG=725653

Review-Url: https://codereview.chromium.org/2906463002
Cr-Original-Commit-Position: refs/heads/master@{#475111}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 0d700dd8b90fd715b2355ad69e5fadfd4fa9eb27
1 file changed