GitLab

https://google.github.io/styleguide/cppguide.html#0_and_nullptr/NULL
says:
"For pointers (address values), use nullptr, as this provides
type-safety."
Furthermore, NULL/0 won't compile if we change |SomeClass*| to
|CheckedPtr<SomeClass>|. See go/miracleptr for more details.

!! is used in situations where the pointer is assigned to or returned
as bool, otherwise CheckedPtr's more costly implicit T* cast operator
would kick in. !! isn't needed in boolean expressions. Examples here:
https://chromium-review.googlesource.com/c/chromium/src/+/2226003

Bug: 1080832
Change-Id: I449817c8949d85bd99a1f7d5043cd189f109303c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2227936
Auto-Submit: Bartek Nowierski <bartekn@chromium.org>
Commit-Queue: Kentaro Hara <haraken@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Cr-Commit-Position: refs/heads/master@{#774523}