This reverts commit b8ffaf4cfcb5e6b6a9916bb1b314820b10b0daf4.

Reason for revert:
This broke the build of the blink_gc_plugin, which does not use base/
(see bug). Please don't commit to tools/clang/ without review.

Original change's description:
> IWYU for bind/callback_helpers.h and ptr_util.h
> 
> These missing includes are preventing removal of unused headers from
> task_runner_util.h and consequently migration from task_runner_util.h to
> task_runner.h's new PostTaskAndReplyWithResult member method.
> 
> The following script was run on every file in the codebase, prioritizing
> .h over matching .cc to best enforce the rule of not include a header
> included by your .h :
> 
> def Fix(file_path):
>   content = refactor_lib.ReadFile(file_path)
> 
>   # Assume fwd-decls are correct in first pass.
>   fwd_decls_match = re.compile(r'\n *[^/\n][^/\n][^/\n]*class (NullCallback|DoNothing|ScopedClosureRunner);', re.DOTALL).findall(content)
>   if fwd_decls_match:
>     print 'fwd_decls_match in %s' % (file_path)
>     return False
> 
>   bind_helpers_match = re.compile(
>       # Doesn't begin with a comment.
>       r'\n *[^/\n][^/\n]'
>       # Anything else after a non-comment start (and don't allow this to capture a comment start either)
>       r'[^/\n]*'
>       # Anything before but an open angle-bracket to avoid cases like unique_ptr<Foo> where you don't need the full definition of Foo.
>       r'[^<]'
>       # Only match with base:: prefix; more precise, can manually fix missing includes in //base proper in a follow-up pass if needed.
>       r'base::(NullCallback|DoNothing|DeletePointer)\b[^*]', re.DOTALL).findall(content)
> 
>   callback_helpers_match = re.compile(r'\n *[^/\n][^/\n][^/\n]*[^<]base::(IsBaseCallback|EnableIfIsBaseCallback|AdaptCallbackForRepeating|ScopedClosureRunner)\b[^*]', re.DOTALL).findall(content)
> 
>   ptr_util_match = re.compile(r'\n *[^/\n][^/\n][^/\n]*[^<]base::WrapUnique\b[^*]', re.DOTALL).findall(content)
> 
>   if not bind_helpers_match and not callback_helpers_match and not ptr_util_match:
>     return False
> 
>   updated_content = content
>   if bind_helpers_match:
>     updated_content = refactor_lib.AddInclude(file_path, updated_content, "base/bind_helpers.h")
>   if callback_helpers_match:
>     updated_content = refactor_lib.AddInclude(file_path, updated_content, "base/callback_helpers.h")
>   if ptr_util_match:
>     updated_content = refactor_lib.AddInclude(file_path, updated_content, "base/memory/ptr_util.h")
> 
>   if updated_content == content:
>     return False
> 
>   # Write updated file
>   refactor_lib.WriteFile(file_path, updated_content)
> 
>   return True
> 
> TBR=danakj@chromium.org
> (mechanical change for //base API)
> 
> Bug: 1026641
> Change-Id: Ic88585c62dd2f74d34c59c708faeddb231aee47f
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2087971


> Reviewed-by: Gabriel Charette <gab@chromium.org>
> Reviewed-by: danakj <danakj@chromium.org>
> Commit-Queue: Gabriel Charette <gab@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#747685}

TBR=danakj@chromium.org,gab@chromium.org

Change-Id: I59d6cd69bd898e9f6d10922c67d8c24ba582bf7f
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 1026641, 1059359
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2091356


Reviewed-by: Hans Wennborg <hans@chromium.org>
Commit-Queue: Hans Wennborg <hans@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#747804}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 7a13e2645a7cd50b0bdfd96e72bcdd9b7e9fee26