Allow std::unordered_*.
base::hash_* is, as a transition step, implemented in terms of
std::unordered_*. Later commits will convert existing uses.
Also fix a host of IWYU problems that arose from this CL.
(NOPRESUBMIT because the wstring presubmit check is overzealous
and complains about the reference to wstring in the comment.)
NOPRESUBMIT=true
BUG=576864
TBR=derat@chromium.org,blundell@chromium.org,jbauman@chromium.org,dalecurtis@chromium.org
CQ_INCLUDE_TRYBOTS=tryserver.blink:linux_blink_rel
Review URL: https://codereview.chromium.org/1502373009
Cr-Commit-Position: refs/heads/master@{#370553}
40 files changed
