Swap from base/stl_util.h to cxx17_backports.h in base/ .cc files.

base::size() has been moved to base/cxx17_backports.h, so .cc files that
use base::size(), but no other function from base/stl_util.h, can
directly include base/cxx17_backports.h and not base/stl_util.h.

Bug: 1210983
Change-Id: Icb506709006e58551123e081f90cc162456cf280
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2957594
Reviewed-by: Wez <[email protected]>
Commit-Queue: Lei Zhang <[email protected]>
Cr-Commit-Position: refs/heads/master@{#892660}
diff --git a/base/containers/intrusive_heap_unittest.cc b/base/containers/intrusive_heap_unittest.cc
index c9804cb..5db6d3b5 100644
--- a/base/containers/intrusive_heap_unittest.cc
+++ b/base/containers/intrusive_heap_unittest.cc
@@ -5,10 +5,10 @@
 #include "base/containers/intrusive_heap.h"
 
 #include "base/check_op.h"
+#include "base/cxx17_backports.h"
 #include "base/memory/ptr_util.h"
 #include "base/notreached.h"
 #include "base/rand_util.h"
-#include "base/stl_util.h"
 #include "testing/gmock/include/gmock/gmock.h"
 #include "testing/gtest/include/gtest/gtest.h"