diff --git base/BUILD.gn base/BUILD.gn
index 20e49fa40d823..9e18a2b2dc6c0 100644
--- base/BUILD.gn
+++ base/BUILD.gn
@@ -37,6 +37,7 @@ import("//build/nocompile.gni")
 import("//build/rust/mixed_component.gni")
 import("//build/timestamp.gni")
 import("//build_overrides/build.gni")
+import("//cef/libcef/features/features.gni")
 import("//testing/libfuzzer/fuzzer_test.gni")
 import("//testing/test.gni")
 
@@ -1957,7 +1958,11 @@ mixed_component("base") {
     "hash/md5_constexpr_internal.h",
     "hash/sha1.h",
   ]
-  if (is_nacl) {
+  deps += [ "//cef/libcef/features" ]
+  if (enable_cef) {
+    configs += [ "//cef/libcef/features:config" ]
+  }
+  if (is_nacl || is_cef_sandbox_build) {
     sources += [
       "hash/md5_nacl.cc",
       "hash/md5_nacl.h",
@@ -2107,6 +2112,12 @@ mixed_component("base") {
       defines += [ "COM_INIT_CHECK_HOOK_DISABLED" ]
     }
 
+    if (!use_custom_libcxx) {
+      # Enable the VS 2015 Update 2 fix when building with the MSVC standard
+      # library.
+      defines += [ "_ENABLE_ATOMIC_ALIGNMENT_FIX" ]
+    }
+
     libs += [
       "cfgmgr32.lib",
       "powrprof.lib",
diff --git base/allocator/dispatcher/dispatcher.cc base/allocator/dispatcher/dispatcher.cc
index b6ecb1c5640ea..892c011336706 100644
--- base/allocator/dispatcher/dispatcher.cc
+++ base/allocator/dispatcher/dispatcher.cc
@@ -13,6 +13,7 @@
 #include "base/dcheck_is_on.h"
 #include "base/no_destructor.h"
 #include "base/sampling_heap_profiler/poisson_allocation_sampler.h"
+#include "cef/libcef/features/features.h"
 
 #if DCHECK_IS_ON()
 #include <atomic>
@@ -260,7 +261,7 @@ struct Dispatcher::Impl {
   }
 
   void Reset() {
-#if DCHECK_IS_ON()
+#if DCHECK_IS_ON() && !BUILDFLAG(IS_CEF_SANDBOX_BUILD)
     DCHECK([&]() {
       auto const was_set = is_initialized_check_flag_.test();
       is_initialized_check_flag_.clear();
diff --git base/hash/md5.h base/hash/md5.h
index ea6bbd31e3fc8..9941050ac0113 100644
--- base/hash/md5.h
+++ base/hash/md5.h
@@ -10,8 +10,9 @@
 #include "base/base_export.h"
 #include "base/strings/string_piece.h"
 #include "build/build_config.h"
+#include "cef/libcef/features/features.h"
 
-#if BUILDFLAG(IS_NACL)
+#if BUILDFLAG(IS_NACL) || BUILDFLAG(IS_CEF_SANDBOX_BUILD)
 #include "base/hash/md5_nacl.h"
 #else
 #include "base/hash/md5_boringssl.h"
diff --git base/hash/sha1.h base/hash/sha1.h
index c4e656b9a68ef..8eb01343cd5d1 100644
--- base/hash/sha1.h
+++ base/hash/sha1.h
@@ -14,7 +14,9 @@
 #include "base/containers/span.h"
 #include "base/strings/string_piece.h"
 #include "build/build_config.h"
-#if BUILDFLAG(IS_NACL)
+#include "cef/libcef/features/features.h"
+
+#if BUILDFLAG(IS_NACL) || BUILDFLAG(IS_CEF_SANDBOX_BUILD)
 #include "base/hash/sha1_nacl.h"
 #else
 #include "base/hash/sha1_boringssl.h"
diff --git base/unguessable_token.cc base/unguessable_token.cc
index 04ea514c6ce35..4f69b8a7f87f3 100644
--- base/unguessable_token.cc
+++ base/unguessable_token.cc
@@ -9,8 +9,9 @@
 #include "base/format_macros.h"
 #include "base/rand_util.h"
 #include "build/build_config.h"
+#include "cef/libcef/features/features.h"
 
-#if !BUILDFLAG(IS_NACL)
+#if !BUILDFLAG(IS_NACL) && !BUILDFLAG(IS_CEF_SANDBOX_BUILD)
 #include "third_party/boringssl/src/include/openssl/mem.h"
 #endif
 
@@ -41,7 +42,7 @@ UnguessableToken UnguessableToken::Deserialize(uint64_t high, uint64_t low) {
 }
 
 bool UnguessableToken::operator==(const UnguessableToken& other) const {
-#if BUILDFLAG(IS_NACL)
+#if BUILDFLAG(IS_NACL) || BUILDFLAG(IS_CEF_SANDBOX_BUILD)
   // BoringSSL is unavailable for NaCl builds so it remains timing dependent.
   return token_ == other.token_;
 #else