diff --git a/core/fpdfapi/edit/cpdf_pagecontentgenerator.h b/core/fpdfapi/edit/cpdf_pagecontentgenerator.h
index dfcd700..0f603f2 100644
--- a/core/fpdfapi/edit/cpdf_pagecontentgenerator.h
+++ b/core/fpdfapi/edit/cpdf_pagecontentgenerator.h
@@ -13,7 +13,7 @@
 #include <vector>
 
 #include "core/fxcrt/bytestring.h"
-#include "core/fxcrt/stl_util.h"
+#include "core/fxcrt/fx_string_wrappers.h"
 #include "core/fxcrt/unowned_ptr.h"
 
 class CPDF_ContentMarks;
diff --git a/core/fpdfapi/edit/cpdf_pagecontentmanager.h b/core/fpdfapi/edit/cpdf_pagecontentmanager.h
index 0249d18..d40c87f 100644
--- a/core/fpdfapi/edit/cpdf_pagecontentmanager.h
+++ b/core/fpdfapi/edit/cpdf_pagecontentmanager.h
@@ -7,8 +7,8 @@
 
 #include <set>
 
+#include "core/fxcrt/fx_string_wrappers.h"
 #include "core/fxcrt/retain_ptr.h"
-#include "core/fxcrt/stl_util.h"
 #include "core/fxcrt/unowned_ptr.h"
 
 class CPDF_Array;
diff --git a/core/fpdfapi/edit/cpdf_stringarchivestream.h b/core/fpdfapi/edit/cpdf_stringarchivestream.h
index 0b0a489..38e6651 100644
--- a/core/fpdfapi/edit/cpdf_stringarchivestream.h
+++ b/core/fpdfapi/edit/cpdf_stringarchivestream.h
@@ -6,7 +6,7 @@
 #define CORE_FPDFAPI_EDIT_CPDF_STRINGARCHIVESTREAM_H_
 
 #include "core/fxcrt/fx_stream.h"
-#include "core/fxcrt/stl_util.h"
+#include "core/fxcrt/fx_string_wrappers.h"
 
 class CPDF_StringArchiveStream final : public IFX_ArchiveStream {
  public:
diff --git a/core/fpdfapi/parser/cfdf_document.cpp b/core/fpdfapi/parser/cfdf_document.cpp
index 5b6510e..13eab14 100644
--- a/core/fpdfapi/parser/cfdf_document.cpp
+++ b/core/fpdfapi/parser/cfdf_document.cpp
@@ -14,7 +14,7 @@
 #include "core/fpdfapi/parser/cpdf_syntax_parser.h"
 #include "core/fpdfapi/parser/fpdf_parser_utility.h"
 #include "core/fxcrt/cfx_readonlymemorystream.h"
-#include "core/fxcrt/stl_util.h"
+#include "core/fxcrt/fx_string_wrappers.h"
 #include "third_party/base/span.h"
 
 CFDF_Document::CFDF_Document() = default;
diff --git a/core/fpdfapi/parser/cpdf_stream.h b/core/fpdfapi/parser/cpdf_stream.h
index bb61f8c..eaf2696 100644
--- a/core/fpdfapi/parser/cpdf_stream.h
+++ b/core/fpdfapi/parser/cpdf_stream.h
@@ -13,8 +13,8 @@
 #include "core/fpdfapi/parser/cpdf_object.h"
 #include "core/fxcrt/fx_memory_wrappers.h"
 #include "core/fxcrt/fx_stream.h"
+#include "core/fxcrt/fx_string_wrappers.h"
 #include "core/fxcrt/retain_ptr.h"
-#include "core/fxcrt/stl_util.h"
 
 class CPDF_Stream final : public CPDF_Object {
  public:
diff --git a/core/fpdfdoc/cpdf_generateap.cpp b/core/fpdfdoc/cpdf_generateap.cpp
index 766d77b..ff876f4 100644
--- a/core/fpdfdoc/cpdf_generateap.cpp
+++ b/core/fpdfdoc/cpdf_generateap.cpp
@@ -33,7 +33,7 @@
 #include "core/fpdfdoc/cpvt_fontmap.h"
 #include "core/fpdfdoc/cpvt_variabletext.h"
 #include "core/fpdfdoc/cpvt_word.h"
-#include "core/fxcrt/stl_util.h"
+#include "core/fxcrt/fx_string_wrappers.h"
 #include "core/fxge/cfx_renderdevice.h"
 
 namespace {
diff --git a/core/fpdfdoc/cpdf_interactiveform.cpp b/core/fpdfdoc/cpdf_interactiveform.cpp
index 36bdae1..9c2fcd1 100644
--- a/core/fpdfdoc/cpdf_interactiveform.cpp
+++ b/core/fpdfdoc/cpdf_interactiveform.cpp
@@ -28,6 +28,7 @@
 #include "core/fpdfdoc/cpdf_filespec.h"
 #include "core/fpdfdoc/cpdf_formcontrol.h"
 #include "core/fxcrt/fx_codepage.h"
+#include "core/fxcrt/stl_util.h"
 #include "core/fxge/cfx_substfont.h"
 #include "core/fxge/fx_font.h"
 #include "third_party/abseil-cpp/absl/types/optional.h"
diff --git a/core/fpdfdoc/cpdf_linklist.cpp b/core/fpdfdoc/cpdf_linklist.cpp
index 0acd1fa..23b324e 100644
--- a/core/fpdfdoc/cpdf_linklist.cpp
+++ b/core/fpdfdoc/cpdf_linklist.cpp
@@ -9,6 +9,7 @@
 #include "core/fpdfapi/page/cpdf_page.h"
 #include "core/fpdfapi/parser/cpdf_array.h"
 #include "core/fpdfapi/parser/cpdf_dictionary.h"
+#include "third_party/base/numerics/safe_conversions.h"
 
 CPDF_LinkList::CPDF_LinkList() = default;
 
diff --git a/core/fpdfdoc/cpdf_nametree.cpp b/core/fpdfdoc/cpdf_nametree.cpp
index dfd4e61..b44353c 100644
--- a/core/fpdfdoc/cpdf_nametree.cpp
+++ b/core/fpdfdoc/cpdf_nametree.cpp
@@ -15,6 +15,7 @@
 #include "core/fpdfapi/parser/cpdf_reference.h"
 #include "core/fpdfapi/parser/cpdf_string.h"
 #include "core/fpdfapi/parser/fpdf_parser_decode.h"
+#include "core/fxcrt/stl_util.h"
 #include "third_party/base/check.h"
 #include "third_party/base/ptr_util.h"
 
diff --git a/core/fpdfdoc/cpdf_structtree.cpp b/core/fpdfdoc/cpdf_structtree.cpp
index 133cf5a..bbac010 100644
--- a/core/fpdfdoc/cpdf_structtree.cpp
+++ b/core/fpdfdoc/cpdf_structtree.cpp
@@ -13,6 +13,7 @@
 #include "core/fpdfapi/parser/cpdf_reference.h"
 #include "core/fpdfdoc/cpdf_numbertree.h"
 #include "core/fpdfdoc/cpdf_structelement.h"
+#include "core/fxcrt/stl_util.h"
 
 namespace {
 
diff --git a/core/fxcrt/BUILD.gn b/core/fxcrt/BUILD.gn
index fb7d04f..9afb408 100644
--- a/core/fxcrt/BUILD.gn
+++ b/core/fxcrt/BUILD.gn
@@ -59,6 +59,7 @@
     "fx_stream.h",
     "fx_string.cpp",
     "fx_string.h",
+    "fx_string_wrappers.h",
     "fx_system.cpp",
     "fx_system.h",
     "fx_types.h",
@@ -165,6 +166,7 @@
     "fx_number_unittest.cpp",
     "fx_random_unittest.cpp",
     "fx_string_unittest.cpp",
+    "fx_string_wrappers_unittest.cpp",
     "fx_system_unittest.cpp",
     "mask_unittest.cpp",
     "maybe_owned_unittest.cpp",
@@ -175,7 +177,6 @@
     "scoped_set_insertion_unittest.cpp",
     "shared_copy_on_write_unittest.cpp",
     "span_util_unittest.cpp",
-    "stl_util_unittest.cpp",
     "string_pool_template_unittest.cpp",
     "tree_node_unittest.cpp",
     "unowned_ptr_unittest.cpp",
diff --git a/core/fxcrt/bytestring.h b/core/fxcrt/bytestring.h
index 830c50b..8798893 100644
--- a/core/fxcrt/bytestring.h
+++ b/core/fxcrt/bytestring.h
@@ -17,8 +17,8 @@
 #include <iterator>
 #include <utility>
 
+#include "core/fxcrt/fx_string_wrappers.h"
 #include "core/fxcrt/retain_ptr.h"
-#include "core/fxcrt/stl_util.h"
 #include "core/fxcrt/string_data_template.h"
 #include "core/fxcrt/string_view_template.h"
 #include "third_party/abseil-cpp/absl/types/optional.h"
diff --git a/core/fxcrt/fx_string_wrappers.h b/core/fxcrt/fx_string_wrappers.h
new file mode 100644
index 0000000..07514bf
--- /dev/null
+++ b/core/fxcrt/fx_string_wrappers.h
@@ -0,0 +1,25 @@
+// Copyright 2022 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 CORE_FXCRT_FX_STRING_WRAPPERS_H_
+#define CORE_FXCRT_FX_STRING_WRAPPERS_H_
+
+#include <iosfwd>
+#include <string>
+
+#include "core/fxcrt/fx_memory_wrappers.h"
+
+namespace fxcrt {
+
+// String that uses partition alloc for backing store.
+using string =
+    std::basic_string<char, std::char_traits<char>, FxStringAllocator<char>>;
+
+// String stream that uses PartitionAlloc for backing store.
+using ostringstream = std::
+    basic_ostringstream<char, std::char_traits<char>, FxStringAllocator<char>>;
+
+}  // namespace fxcrt
+
+#endif  // CORE_FXCRT_FX_STRING_WRAPPERS_H_
diff --git a/core/fxcrt/stl_util_unittest.cpp b/core/fxcrt/fx_string_wrappers_unittest.cpp
similarity index 92%
rename from core/fxcrt/stl_util_unittest.cpp
rename to core/fxcrt/fx_string_wrappers_unittest.cpp
index ab291a3..788e608 100644
--- a/core/fxcrt/stl_util_unittest.cpp
+++ b/core/fxcrt/fx_string_wrappers_unittest.cpp
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include "core/fxcrt/stl_util.h"
+#include "core/fxcrt/fx_string_wrappers.h"
 
 #include "testing/gtest/include/gtest/gtest.h"
 
diff --git a/core/fxcrt/stl_util.h b/core/fxcrt/stl_util.h
index 7b76f5e..37156af 100644
--- a/core/fxcrt/stl_util.h
+++ b/core/fxcrt/stl_util.h
@@ -5,12 +5,9 @@
 #ifndef CORE_FXCRT_STL_UTIL_H_
 #define CORE_FXCRT_STL_UTIL_H_
 
-#include <iosfwd>
 #include <memory>
-#include <string>
 #include <vector>
 
-#include "core/fxcrt/fx_memory_wrappers.h"
 #include "third_party/base/numerics/safe_conversions.h"
 #include "third_party/base/numerics/safe_math.h"
 
@@ -47,14 +44,6 @@
   return std::vector<T, A>(safe_size.ValueOrDie());
 }
 
-// String that uses partition alloc for backing store.
-using string =
-    std::basic_string<char, std::char_traits<char>, FxStringAllocator<char>>;
-
-// String stream that uses PartitionAlloc for backing store.
-using ostringstream = std::
-    basic_ostringstream<char, std::char_traits<char>, FxStringAllocator<char>>;
-
 }  // namespace fxcrt
 
 #endif  // CORE_FXCRT_STL_UTIL_H_
diff --git a/core/fxge/win32/cfx_psrenderer.h b/core/fxge/win32/cfx_psrenderer.h
index 49d3542..be88677 100644
--- a/core/fxge/win32/cfx_psrenderer.h
+++ b/core/fxge/win32/cfx_psrenderer.h
@@ -18,8 +18,8 @@
 #include "core/fxcrt/fx_coordinates.h"
 #include "core/fxcrt/fx_memory_wrappers.h"
 #include "core/fxcrt/fx_stream.h"
+#include "core/fxcrt/fx_string_wrappers.h"
 #include "core/fxcrt/retain_ptr.h"
-#include "core/fxcrt/stl_util.h"
 #include "core/fxcrt/unowned_ptr.h"
 #include "core/fxge/cfx_graphstatedata.h"
 #include "third_party/abseil-cpp/absl/types/optional.h"
diff --git a/core/fxge/win32/cgdi_plus_ext.cpp b/core/fxge/win32/cgdi_plus_ext.cpp
index 7dffd0e..22297c4 100644
--- a/core/fxge/win32/cgdi_plus_ext.cpp
+++ b/core/fxge/win32/cgdi_plus_ext.cpp
@@ -17,8 +17,8 @@
 
 #include "core/fxcrt/fx_memory.h"
 #include "core/fxcrt/fx_string.h"
+#include "core/fxcrt/fx_string_wrappers.h"
 #include "core/fxcrt/fx_system.h"
-#include "core/fxcrt/stl_util.h"
 #include "core/fxge/cfx_fillrenderoptions.h"
 #include "core/fxge/cfx_gemodule.h"
 #include "core/fxge/cfx_graphstatedata.h"
diff --git a/fpdfsdk/cpdfsdk_appstream.cpp b/fpdfsdk/cpdfsdk_appstream.cpp
index 8e884e9..870bac4 100644
--- a/fpdfsdk/cpdfsdk_appstream.cpp
+++ b/fpdfsdk/cpdfsdk_appstream.cpp
@@ -27,6 +27,7 @@
 #include "core/fpdfdoc/cpdf_formcontrol.h"
 #include "core/fpdfdoc/cpdf_icon.h"
 #include "core/fpdfdoc/cpvt_word.h"
+#include "core/fxcrt/fx_string_wrappers.h"
 #include "fpdfsdk/cpdfsdk_formfillenvironment.h"
 #include "fpdfsdk/cpdfsdk_interactiveform.h"
 #include "fpdfsdk/cpdfsdk_pageview.h"
diff --git a/fpdfsdk/cpdfsdk_interactiveform.cpp b/fpdfsdk/cpdfsdk_interactiveform.cpp
index 892954e..696e16c 100644
--- a/fpdfsdk/cpdfsdk_interactiveform.cpp
+++ b/fpdfsdk/cpdfsdk_interactiveform.cpp
@@ -23,7 +23,7 @@
 #include "core/fpdfdoc/cpdf_formcontrol.h"
 #include "core/fpdfdoc/cpdf_interactiveform.h"
 #include "core/fxcrt/autorestorer.h"
-#include "core/fxcrt/stl_util.h"
+#include "core/fxcrt/fx_string_wrappers.h"
 #include "core/fxge/cfx_graphstatedata.h"
 #include "core/fxge/cfx_path.h"
 #include "fpdfsdk/cpdfsdk_actionhandler.h"
diff --git a/fpdfsdk/fpdf_annot.cpp b/fpdfsdk/fpdf_annot.cpp
index 1feead8..2dd52b2 100644
--- a/fpdfsdk/fpdf_annot.cpp
+++ b/fpdfsdk/fpdf_annot.cpp
@@ -30,6 +30,7 @@
 #include "core/fpdfdoc/cpdf_generateap.h"
 #include "core/fpdfdoc/cpdf_interactiveform.h"
 #include "core/fxcrt/fx_safe_types.h"
+#include "core/fxcrt/fx_string_wrappers.h"
 #include "core/fxcrt/stl_util.h"
 #include "core/fxge/cfx_color.h"
 #include "fpdfsdk/cpdfsdk_formfillenvironment.h"
diff --git a/fpdfsdk/fpdf_edittext.cpp b/fpdfsdk/fpdf_edittext.cpp
index 3f84e09..c2fda59 100644
--- a/fpdfsdk/fpdf_edittext.cpp
+++ b/fpdfsdk/fpdf_edittext.cpp
@@ -24,6 +24,7 @@
 #include "core/fpdfapi/render/charposlist.h"
 #include "core/fpdftext/cpdf_textpage.h"
 #include "core/fxcrt/fx_extension.h"
+#include "core/fxcrt/fx_string_wrappers.h"
 #include "core/fxcrt/stl_util.h"
 #include "core/fxge/cfx_fontmgr.h"
 #include "core/fxge/fx_font.h"
diff --git a/fpdfsdk/fpdf_flatten.cpp b/fpdfsdk/fpdf_flatten.cpp
index 348a325..1efb188 100644
--- a/fpdfsdk/fpdf_flatten.cpp
+++ b/fpdfsdk/fpdf_flatten.cpp
@@ -28,7 +28,7 @@
 #include "core/fpdfapi/parser/cpdf_stream.h"
 #include "core/fpdfapi/parser/cpdf_stream_acc.h"
 #include "core/fpdfdoc/cpdf_annot.h"
-#include "core/fxcrt/stl_util.h"
+#include "core/fxcrt/fx_string_wrappers.h"
 #include "fpdfsdk/cpdfsdk_helpers.h"
 #include "third_party/base/notreached.h"
 
diff --git a/fpdfsdk/fpdf_ppo.cpp b/fpdfsdk/fpdf_ppo.cpp
index 1a7531c..ec42c90 100644
--- a/fpdfsdk/fpdf_ppo.cpp
+++ b/fpdfsdk/fpdf_ppo.cpp
@@ -31,6 +31,7 @@
 #include "core/fpdfapi/parser/cpdf_string.h"
 #include "core/fpdfapi/render/cpdf_pagerendercache.h"
 #include "core/fxcrt/fx_safe_types.h"
+#include "core/fxcrt/fx_string_wrappers.h"
 #include "core/fxcrt/retain_ptr.h"
 #include "core/fxcrt/unowned_ptr.h"
 #include "fpdfsdk/cpdfsdk_helpers.h"
diff --git a/fpdfsdk/fpdf_structtree.cpp b/fpdfsdk/fpdf_structtree.cpp
index 538ad2e..76fd601 100644
--- a/fpdfsdk/fpdf_structtree.cpp
+++ b/fpdfsdk/fpdf_structtree.cpp
@@ -12,6 +12,7 @@
 #include "core/fpdfdoc/cpdf_structelement.h"
 #include "core/fpdfdoc/cpdf_structtree.h"
 #include "core/fxcrt/fx_safe_types.h"
+#include "core/fxcrt/stl_util.h"
 #include "fpdfsdk/cpdfsdk_helpers.h"
 
 namespace {
diff --git a/fpdfsdk/fpdf_transformpage.cpp b/fpdfsdk/fpdf_transformpage.cpp
index e142166..ea41d00 100644
--- a/fpdfsdk/fpdf_transformpage.cpp
+++ b/fpdfsdk/fpdf_transformpage.cpp
@@ -21,6 +21,7 @@
 #include "core/fpdfapi/parser/cpdf_number.h"
 #include "core/fpdfapi/parser/cpdf_reference.h"
 #include "core/fpdfapi/parser/cpdf_stream.h"
+#include "core/fxcrt/fx_string_wrappers.h"
 #include "core/fxcrt/stl_util.h"
 #include "core/fxge/cfx_fillrenderoptions.h"
 #include "core/fxge/cfx_path.h"
diff --git a/fxjs/cjs_publicmethods.cpp b/fxjs/cjs_publicmethods.cpp
index dce96c4..503d868 100644
--- a/fxjs/cjs_publicmethods.cpp
+++ b/fxjs/cjs_publicmethods.cpp
@@ -21,7 +21,7 @@
 #include "core/fpdfdoc/cpdf_formcontrol.h"
 #include "core/fpdfdoc/cpdf_interactiveform.h"
 #include "core/fxcrt/fx_extension.h"
-#include "core/fxcrt/stl_util.h"
+#include "core/fxcrt/fx_string_wrappers.h"
 #include "core/fxge/cfx_color.h"
 #include "fpdfsdk/cpdfsdk_formfillenvironment.h"
 #include "fpdfsdk/cpdfsdk_interactiveform.h"
diff --git a/fxjs/xfa/cjx_field.cpp b/fxjs/xfa/cjx_field.cpp
index 8352247..854471e 100644
--- a/fxjs/xfa/cjx_field.cpp
+++ b/fxjs/xfa/cjx_field.cpp
@@ -11,6 +11,7 @@
 #include "fxjs/cfx_v8.h"
 #include "fxjs/fxv8.h"
 #include "fxjs/js_resources.h"
+#include "third_party/base/numerics/safe_conversions.h"
 #include "v8/include/v8-primitive.h"
 #include "xfa/fgas/crt/cfgas_decimal.h"
 #include "xfa/fxfa/cxfa_eventparam.h"