Revert "Separate preaload matching from MemoryCache"

This CL reverts [1] due to performance regressions.

1: https://chromium.googlesource.com/chromium/src/+/bb924e1897f5b4c67325dbfbdf2441e7f0686d53

BUG=695939, 719502
TBR=japhet@chromium.org

Review-Url: https://codereview.chromium.org/2867333002
Cr-Commit-Position: refs/heads/master@{#470825}
11 files changed