Fix hang_watcher's standard lib header includes.

BUG=None
TEST=Build locally.

Change-Id: Ibf130dcb59c094cedb6fc94ed62f74d97a299616
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2029406
Commit-Queue: Hidehiko Abe <hidehiko@chromium.org>
Commit-Queue: François Doray <fdoray@chromium.org>
Reviewed-by: François Doray <fdoray@chromium.org>
Cr-Commit-Position: refs/heads/master@{#736877}

base/threading/hang_watcher.cc

@@ -3,6 +3,10 @@
 // found in the LICENSE file.
 
 #include "base/threading/hang_watcher.h"
+
+#include <algorithm>
+#include <utility>
+
 #include "base/bind.h"
 #include "base/callback_helpers.h"
 #include "base/no_destructor.h"

base/threading/hang_watcher.h

@@ -5,8 +5,9 @@
 #ifndef BASE_THREADING_HANG_WATCHER_H_
 #define BASE_THREADING_HANG_WATCHER_H_
 
-#include <exception>
+#include <atomic>
 #include <memory>
+#include <vector>
 
 #include "base/atomicops.h"
 #include "base/callback.h"