diff --git a/core/fpdfapi/font/cpdf_cidfont.cpp b/core/fpdfapi/font/cpdf_cidfont.cpp
index 9785aca..b05bfbc 100644
--- a/core/fpdfapi/font/cpdf_cidfont.cpp
+++ b/core/fpdfapi/font/cpdf_cidfont.cpp
@@ -28,6 +28,7 @@
 #include "third_party/base/check.h"
 #include "third_party/base/check_op.h"
 #include "third_party/base/cxx17_backports.h"
+#include "third_party/base/numerics/ranges.h"
 #include "third_party/base/span.h"
 #include "third_party/base/stl_util.h"
 
diff --git a/core/fpdfapi/font/cpdf_font.cpp b/core/fpdfapi/font/cpdf_font.cpp
index c6ea201..8edccbd 100644
--- a/core/fpdfapi/font/cpdf_font.cpp
+++ b/core/fpdfapi/font/cpdf_font.cpp
@@ -31,6 +31,7 @@
 #include "core/fxge/fx_freetype.h"
 #include "third_party/base/check.h"
 #include "third_party/base/cxx17_backports.h"
+#include "third_party/base/numerics/ranges.h"
 #include "third_party/base/stl_util.h"
 
 namespace {
diff --git a/core/fpdfapi/page/cpdf_allstates.cpp b/core/fpdfapi/page/cpdf_allstates.cpp
index a12ce33..4b92510 100644
--- a/core/fpdfapi/page/cpdf_allstates.cpp
+++ b/core/fpdfapi/page/cpdf_allstates.cpp
@@ -18,7 +18,7 @@
 #include "core/fpdfapi/parser/fpdf_parser_utility.h"
 #include "core/fxge/cfx_graphstatedata.h"
 #include "third_party/base/compiler_specific.h"
-#include "third_party/base/stl_util.h"
+#include "third_party/base/numerics/ranges.h"
 
 CPDF_AllStates::CPDF_AllStates() = default;
 
diff --git a/core/fpdfapi/page/cpdf_colorspace.cpp b/core/fpdfapi/page/cpdf_colorspace.cpp
index 6f07ba3..0ff6718 100644
--- a/core/fpdfapi/page/cpdf_colorspace.cpp
+++ b/core/fpdfapi/page/cpdf_colorspace.cpp
@@ -39,6 +39,7 @@
 #include "third_party/base/containers/contains.h"
 #include "third_party/base/cxx17_backports.h"
 #include "third_party/base/notreached.h"
+#include "third_party/base/numerics/ranges.h"
 #include "third_party/base/stl_util.h"
 
 namespace {
diff --git a/core/fpdfapi/page/cpdf_devicecs.cpp b/core/fpdfapi/page/cpdf_devicecs.cpp
index 25fefe0..2a5a336 100644
--- a/core/fpdfapi/page/cpdf_devicecs.cpp
+++ b/core/fpdfapi/page/cpdf_devicecs.cpp
@@ -17,7 +17,7 @@
 #include "core/fxge/dib/cfx_cmyk_to_srgb.h"
 #include "third_party/base/check.h"
 #include "third_party/base/notreached.h"
-#include "third_party/base/stl_util.h"
+#include "third_party/base/numerics/ranges.h"
 
 namespace {
 
diff --git a/core/fpdfapi/page/cpdf_dib.cpp b/core/fpdfapi/page/cpdf_dib.cpp
index 70bde5f..996a856 100644
--- a/core/fpdfapi/page/cpdf_dib.cpp
+++ b/core/fpdfapi/page/cpdf_dib.cpp
@@ -35,7 +35,7 @@
 #include "core/fxge/dib/cfx_dibitmap.h"
 #include "third_party/base/check.h"
 #include "third_party/base/check_op.h"
-#include "third_party/base/stl_util.h"
+#include "third_party/base/numerics/ranges.h"
 
 namespace {
 
diff --git a/core/fpdfapi/page/cpdf_function.cpp b/core/fpdfapi/page/cpdf_function.cpp
index 81abfc4..5011cdc 100644
--- a/core/fpdfapi/page/cpdf_function.cpp
+++ b/core/fpdfapi/page/cpdf_function.cpp
@@ -19,7 +19,7 @@
 #include "core/fxcrt/fx_safe_types.h"
 #include "core/fxcrt/scoped_set_insertion.h"
 #include "third_party/base/containers/contains.h"
-#include "third_party/base/stl_util.h"
+#include "third_party/base/numerics/ranges.h"
 
 namespace {
 
diff --git a/core/fpdfapi/page/cpdf_sampledfunc.cpp b/core/fpdfapi/page/cpdf_sampledfunc.cpp
index 05c0148..297ffd0 100644
--- a/core/fpdfapi/page/cpdf_sampledfunc.cpp
+++ b/core/fpdfapi/page/cpdf_sampledfunc.cpp
@@ -13,7 +13,7 @@
 #include "core/fxcrt/cfx_bitstream.h"
 #include "core/fxcrt/cfx_fixedbufgrow.h"
 #include "core/fxcrt/fx_safe_types.h"
-#include "third_party/base/stl_util.h"
+#include "third_party/base/numerics/ranges.h"
 
 namespace {
 
diff --git a/core/fpdfapi/render/cpdf_imagerenderer.cpp b/core/fpdfapi/render/cpdf_imagerenderer.cpp
index de44d41..0728434 100644
--- a/core/fpdfapi/render/cpdf_imagerenderer.cpp
+++ b/core/fpdfapi/render/cpdf_imagerenderer.cpp
@@ -37,7 +37,7 @@
 #include "core/fxge/dib/cfx_imagetransformer.h"
 #include "third_party/base/check.h"
 #include "third_party/base/notreached.h"
-#include "third_party/base/stl_util.h"
+#include "third_party/base/numerics/ranges.h"
 
 #if defined(_SKIA_SUPPORT_)
 #include "core/fxge/skia/fx_skia_device.h"
diff --git a/core/fpdfdoc/cpvt_section.cpp b/core/fpdfdoc/cpvt_section.cpp
index acd479c..41318ea 100644
--- a/core/fpdfdoc/cpvt_section.cpp
+++ b/core/fpdfdoc/cpvt_section.cpp
@@ -11,6 +11,7 @@
 #include "core/fpdfdoc/cpvt_variabletext.h"
 #include "core/fpdfdoc/cpvt_wordinfo.h"
 #include "third_party/base/check.h"
+#include "third_party/base/numerics/ranges.h"
 #include "third_party/base/stl_util.h"
 
 namespace {
diff --git a/core/fpdfdoc/cpvt_variabletext.cpp b/core/fpdfdoc/cpvt_variabletext.cpp
index df7408a..e458e94 100644
--- a/core/fpdfdoc/cpvt_variabletext.cpp
+++ b/core/fpdfdoc/cpvt_variabletext.cpp
@@ -17,6 +17,7 @@
 #include "core/fxcrt/fx_codepage.h"
 #include "third_party/base/check.h"
 #include "third_party/base/compiler_specific.h"
+#include "third_party/base/numerics/ranges.h"
 #include "third_party/base/stl_util.h"
 
 namespace {
diff --git a/core/fxcodec/fax/faxmodule.cpp b/core/fxcodec/fax/faxmodule.cpp
index 0e652b8..9129249 100644
--- a/core/fxcodec/fax/faxmodule.cpp
+++ b/core/fxcodec/fax/faxmodule.cpp
@@ -18,6 +18,7 @@
 #include "core/fxcrt/fx_memory_wrappers.h"
 #include "third_party/base/check.h"
 #include "third_party/base/check_op.h"
+#include "third_party/base/numerics/ranges.h"
 #include "third_party/base/stl_util.h"
 
 namespace fxcodec {
diff --git a/core/fxcodec/icc/iccmodule.cpp b/core/fxcodec/icc/iccmodule.cpp
index 4e20647..acdb7b1 100644
--- a/core/fxcodec/icc/iccmodule.cpp
+++ b/core/fxcodec/icc/iccmodule.cpp
@@ -12,7 +12,7 @@
 
 #include "core/fxcrt/fx_memory_wrappers.h"
 #include "third_party/base/notreached.h"
-#include "third_party/base/stl_util.h"
+#include "third_party/base/numerics/ranges.h"
 
 namespace fxcodec {
 
diff --git a/core/fxcodec/jpx/cjpx_decoder.cpp b/core/fxcodec/jpx/cjpx_decoder.cpp
index 6ed54ea..c871977 100644
--- a/core/fxcodec/jpx/cjpx_decoder.cpp
+++ b/core/fxcodec/jpx/cjpx_decoder.cpp
@@ -13,9 +13,9 @@
 
 #include "core/fxcodec/jpx/jpx_decode_utils.h"
 #include "core/fxcrt/fx_safe_types.h"
+#include "third_party/base/numerics/ranges.h"
 #include "third_party/base/optional.h"
 #include "third_party/base/ptr_util.h"
-#include "third_party/base/stl_util.h"
 
 #if !defined(USE_SYSTEM_LIBOPENJPEG2)
 #include "third_party/libopenjpeg20/opj_malloc.h"
diff --git a/core/fxcrt/bytestring.cpp b/core/fxcrt/bytestring.cpp
index 8046b2a..4a3fa7f 100644
--- a/core/fxcrt/bytestring.cpp
+++ b/core/fxcrt/bytestring.cpp
@@ -21,9 +21,9 @@
 #include "core/fxcrt/string_pool_template.h"
 #include "third_party/base/check.h"
 #include "third_party/base/check_op.h"
+#include "third_party/base/numerics/ranges.h"
 #include "third_party/base/numerics/safe_math.h"
 #include "third_party/base/span.h"
-#include "third_party/base/stl_util.h"
 
 template class fxcrt::StringDataTemplate<char>;
 template class fxcrt::StringViewTemplate<char>;
diff --git a/core/fxcrt/cfx_seekablestreamproxy.cpp b/core/fxcrt/cfx_seekablestreamproxy.cpp
index 78c2e1a..f677eec 100644
--- a/core/fxcrt/cfx_seekablestreamproxy.cpp
+++ b/core/fxcrt/cfx_seekablestreamproxy.cpp
@@ -18,7 +18,7 @@
 #include "core/fxcrt/fx_safe_types.h"
 #include "third_party/base/check.h"
 #include "third_party/base/check_op.h"
-#include "third_party/base/stl_util.h"
+#include "third_party/base/numerics/ranges.h"
 
 namespace {
 
diff --git a/core/fxcrt/widestring.cpp b/core/fxcrt/widestring.cpp
index ee148fd..a69658a 100644
--- a/core/fxcrt/widestring.cpp
+++ b/core/fxcrt/widestring.cpp
@@ -18,8 +18,8 @@
 #include "core/fxcrt/string_pool_template.h"
 #include "third_party/base/check.h"
 #include "third_party/base/check_op.h"
+#include "third_party/base/numerics/ranges.h"
 #include "third_party/base/numerics/safe_math.h"
-#include "third_party/base/stl_util.h"
 
 template class fxcrt::StringDataTemplate<wchar_t>;
 template class fxcrt::StringViewTemplate<wchar_t>;
diff --git a/core/fxge/agg/fx_agg_driver.cpp b/core/fxge/agg/fx_agg_driver.cpp
index 05343f2..ad7a9562 100644
--- a/core/fxge/agg/fx_agg_driver.cpp
+++ b/core/fxge/agg/fx_agg_driver.cpp
@@ -20,8 +20,8 @@
 #include "third_party/base/check.h"
 #include "third_party/base/check_op.h"
 #include "third_party/base/notreached.h"
+#include "third_party/base/numerics/ranges.h"
 #include "third_party/base/span.h"
-#include "third_party/base/stl_util.h"
 
 // Ignore fallthrough warnings in agg23 headers.
 #if defined(__clang__)
diff --git a/core/fxge/dib/cstretchengine.cpp b/core/fxge/dib/cstretchengine.cpp
index ade1c81..a0674cc 100644
--- a/core/fxge/dib/cstretchengine.cpp
+++ b/core/fxge/dib/cstretchengine.cpp
@@ -18,7 +18,7 @@
 #include "core/fxge/dib/fx_dib.h"
 #include "core/fxge/dib/scanlinecomposer_iface.h"
 #include "third_party/base/check.h"
-#include "third_party/base/stl_util.h"
+#include "third_party/base/numerics/ranges.h"
 
 static_assert(
     std::is_trivially_destructible<CStretchEngine::PixelWeight>::value,
diff --git a/core/fxge/skia/fx_skia_device.cpp b/core/fxge/skia/fx_skia_device.cpp
index adb3596..0b092bc 100644
--- a/core/fxge/skia/fx_skia_device.cpp
+++ b/core/fxge/skia/fx_skia_device.cpp
@@ -36,9 +36,9 @@
 #include "third_party/base/check.h"
 #include "third_party/base/check_op.h"
 #include "third_party/base/notreached.h"
+#include "third_party/base/numerics/ranges.h"
 #include "third_party/base/ptr_util.h"
 #include "third_party/base/span.h"
-#include "third_party/base/stl_util.h"
 #include "third_party/skia/include/core/SkBitmap.h"
 #include "third_party/skia/include/core/SkCanvas.h"
 #include "third_party/skia/include/core/SkClipOp.h"
diff --git a/fpdfsdk/formfiller/cffl_interactiveformfiller.cpp b/fpdfsdk/formfiller/cffl_interactiveformfiller.cpp
index b5e1643..9e0b1fe 100644
--- a/fpdfsdk/formfiller/cffl_interactiveformfiller.cpp
+++ b/fpdfsdk/formfiller/cffl_interactiveformfiller.cpp
@@ -26,7 +26,7 @@
 #include "public/fpdf_fwlevent.h"
 #include "third_party/base/check.h"
 #include "third_party/base/check_op.h"
-#include "third_party/base/stl_util.h"
+#include "third_party/base/numerics/ranges.h"
 
 CFFL_InteractiveFormFiller::CFFL_InteractiveFormFiller(
     CPDFSDK_FormFillEnvironment* pFormFillEnv)
diff --git a/fpdfsdk/fpdf_editpage.cpp b/fpdfsdk/fpdf_editpage.cpp
index b21ebfc..286beb9 100644
--- a/fpdfsdk/fpdf_editpage.cpp
+++ b/fpdfsdk/fpdf_editpage.cpp
@@ -36,7 +36,7 @@
 #include "fpdfsdk/cpdfsdk_helpers.h"
 #include "public/fpdf_formfill.h"
 #include "third_party/base/notreached.h"
-#include "third_party/base/stl_util.h"
+#include "third_party/base/numerics/ranges.h"
 
 #ifdef PDF_ENABLE_XFA
 #include "fpdfsdk/fpdfxfa/cpdfxfa_context.h"
diff --git a/fxjs/xfa/cfxjse_formcalc_context.cpp b/fxjs/xfa/cfxjse_formcalc_context.cpp
index 17ff8ad..2669d41 100644
--- a/fxjs/xfa/cfxjse_formcalc_context.cpp
+++ b/fxjs/xfa/cfxjse_formcalc_context.cpp
@@ -25,8 +25,8 @@
 #include "fxjs/xfa/cjx_object.h"
 #include "third_party/base/check.h"
 #include "third_party/base/cxx17_backports.h"
+#include "third_party/base/numerics/ranges.h"
 #include "third_party/base/optional.h"
-#include "third_party/base/stl_util.h"
 #include "xfa/fgas/crt/cfgas_decimal.h"
 #include "xfa/fxfa/cxfa_ffnotify.h"
 #include "xfa/fxfa/fm2js/cxfa_fmparser.h"
diff --git a/third_party/BUILD.gn b/third_party/BUILD.gn
index cdb797c..42c8299 100644
--- a/third_party/BUILD.gn
+++ b/third_party/BUILD.gn
@@ -609,6 +609,7 @@
     "base/numerics/checked_math_impl.h",
     "base/numerics/clamped_math.h",
     "base/numerics/clamped_math_impl.h",
+    "base/numerics/ranges.h",
     "base/numerics/safe_conversions.h",
     "base/numerics/safe_conversions_arm_impl.h",
     "base/numerics/safe_conversions_impl.h",
diff --git a/third_party/base/numerics/ranges.h b/third_party/base/numerics/ranges.h
new file mode 100644
index 0000000..a405e03
--- /dev/null
+++ b/third_party/base/numerics/ranges.h
@@ -0,0 +1,20 @@
+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef THIRD_PARTY_BASE_NUMERICS_RANGES_H_
+#define THIRD_PARTY_BASE_NUMERICS_RANGES_H_
+
+#include <algorithm>
+
+namespace pdfium {
+
+// To be replaced with std::clamp() from C++17, someday.
+template <class T>
+constexpr const T& clamp(const T& value, const T& min, const T& max) {
+  return std::min(std::max(value, min), max);
+}
+
+}  // namespace pdfium
+
+#endif  // THIRD_PARTY_BASE_NUMERICS_RANGES_H_
diff --git a/third_party/base/stl_util.h b/third_party/base/stl_util.h
index 453ee2e..f831ee5 100644
--- a/third_party/base/stl_util.h
+++ b/third_party/base/stl_util.h
@@ -5,7 +5,6 @@
 #ifndef THIRD_PARTY_BASE_STL_UTIL_H_
 #define THIRD_PARTY_BASE_STL_UTIL_H_
 
-#include <algorithm>
 #include <memory>
 #include <vector>
 
@@ -37,12 +36,6 @@
   return index >= 0 && index < CollectionSize<IndexType>(collection);
 }
 
-// std::clamp(), some day.
-template <class T>
-constexpr const T& clamp(const T& v, const T& lo, const T& hi) {
-  return std::min(std::max(v, lo), hi);
-}
-
 // Safely allocate a 1-dim vector big enough for |w| by |h| or die.
 template <typename T, typename A = std::allocator<T>>
 std::vector<T, A> Vector2D(size_t w, size_t h) {
diff --git a/xfa/fwl/cfwl_edit.cpp b/xfa/fwl/cfwl_edit.cpp
index 0e51114..c7a33fb 100644
--- a/xfa/fwl/cfwl_edit.cpp
+++ b/xfa/fwl/cfwl_edit.cpp
@@ -15,7 +15,7 @@
 #include "core/fxge/cfx_renderdevice.h"
 #include "core/fxge/text_char_pos.h"
 #include "third_party/base/check.h"
-#include "third_party/base/stl_util.h"
+#include "third_party/base/numerics/ranges.h"
 #include "v8/include/cppgc/visitor.h"
 #include "xfa/fde/cfde_textout.h"
 #include "xfa/fgas/font/cfgas_gefont.h"
diff --git a/xfa/fwl/cfwl_listbox.cpp b/xfa/fwl/cfwl_listbox.cpp
index 613cc16..7306225 100644
--- a/xfa/fwl/cfwl_listbox.cpp
+++ b/xfa/fwl/cfwl_listbox.cpp
@@ -10,6 +10,7 @@
 #include <memory>
 #include <utility>
 
+#include "third_party/base/numerics/ranges.h"
 #include "third_party/base/stl_util.h"
 #include "v8/include/cppgc/visitor.h"
 #include "xfa/fde/cfde_textout.h"
diff --git a/xfa/fwl/cfwl_scrollbar.cpp b/xfa/fwl/cfwl_scrollbar.cpp
index 8fb01f9..cc5a101 100644
--- a/xfa/fwl/cfwl_scrollbar.cpp
+++ b/xfa/fwl/cfwl_scrollbar.cpp
@@ -10,7 +10,7 @@
 #include <memory>
 #include <utility>
 
-#include "third_party/base/stl_util.h"
+#include "third_party/base/numerics/ranges.h"
 #include "xfa/fwl/cfwl_app.h"
 #include "xfa/fwl/cfwl_messagemouse.h"
 #include "xfa/fwl/cfwl_messagemousewheel.h"