Introduce an ObserverList<T>::Unchecked type alias.

This is a precursor to https://crrev.com/c/1053338 which introduces
base::CheckedObserver. Existing observers will be unchecked (as they
are already). There is no behavior change with this CL.

The CL is mechanical. The bulk was done with variations on a sed script:

git grep -l ' base::ObserverList<.*> .*;' -- '*.cc' '*.h' '*.mm' | \
  xargs -IX sed -i -r 's/(^[ ]*)base::ObserverList<([^>]*)> (.*);/'\
    '\1base::ObserverList<\2>::Unchecked \3;/' X

With some manual follow-ups to get special cases.

TBR=gab@chromium.org

Bug: 842987
Cq-Include-Trybots: luci.chromium.try:android_optional_gpu_tests_rel;luci.chromium.try:ios-simulator-full-configs;luci.chromium.try:linux_layout_tests_slimming_paint_v2;luci.chromium.try:linux_mojo;luci.chromium.try:linux_optional_gpu_tests_rel;luci.chromium.try:mac_optional_gpu_tests_rel;luci.chromium.try:win_optional_gpu_tests_rel;master.tryserver.blink:linux_trusty_blink_rel;master.tryserver.chromium.mac:ios-simulator-cronet
Change-Id: Idffe88e2b52f67f9226eb7b6d922070349dacc22
Reviewed-on: https://chromium-review.googlesource.com/1175511
Commit-Queue: Trent Apted <tapted@chromium.org>
Reviewed-by: Gabriel Charette <gab@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#584330}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: a250ec3ab9e982d9618127273c54dab7e56ff9ba
2 files changed