[cr144] Migrate MD5 usage in default protocol handler to crypto/obsolete/md5.h

Chromium changes:
https://chromium.googlesource.com/chromium/src/+/30e187d7d78b64c59c52a747b5373cc21b389871

commit 30e187d7d78b64c59c52a747b5373cc21b389871
Author: Giovanni Ortuño Urquidi <ortuno@chromium.org>
Date:   Tue Nov 4 09:44:08 2025 -0800

    Remove base/hash/md5.h

    All usages have been migrated to crypto/obsolete/md5.h or upgraded to
    SHA-256.

    Fixed: 406729261
    Change-Id: Ie643451d670c0ab701cddf2b3e820d50debd571e
    Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/7113738
    Reviewed-by: Elly FJ <ellyjones@chromium.org>
    Commit-Queue: Giovanni Ortuno Urquidi <ortuno@chromium.org>
    Reviewed-by: Nico Weber <thakis@chromium.org>
    Owners-Override: Nico Weber <thakis@chromium.org>
    Cr-Commit-Position: refs/heads/main@{#1540135}

browser/default_protocol_handler_utils_win.cc

@@ -21,7 +21,6 @@
 #include "base/containers/span.h"
 #include "base/containers/span_reader.h"
 #include "base/files/file_path.h"
-#include "base/hash/md5.h"
 #include "base/logging.h"
 #include "base/notreached.h"
 #include "base/numerics/byte_conversions.h"
@@ -40,11 +39,19 @@
 #include "base/win/windows_version.h"
 #include "chrome/install_static/install_util.h"
 #include "chrome/installer/util/shell_util.h"
+#include "crypto/obsolete/md5.h"
 #include "third_party/abseil-cpp/absl/strings/str_format.h"
 
 // Most of source code in this file comes from firefox's SetDefaultBrowser -
 // https://github.com/mozilla/gecko-dev/blob/master/toolkit/mozapps/defaultagent/SetDefaultBrowser.cpp
 
+namespace brave {
+std::array<uint8_t, crypto::obsolete::kMd5Size> Md5ForDefaultProtocolHandler(
+    base::span<const uint8_t> data) {
+  return crypto::obsolete::Md5::Hash(data);
+}
+}  // namespace brave
+
 namespace protocol_handler_utils {
 
 namespace {
@@ -67,9 +74,9 @@ std::wstring HashString(base::wcstring_view input) {
 
   // Compute an MD5 hash. md5[0] and md5[1] will be used as constant multipliers
   // in the scramble below.
-  base::MD5Digest digest;
-  base::MD5Sum(bytes, &digest);
-  auto md5 = base::as_byte_span(digest.a).first<8u>();
+  std::array<uint8_t, crypto::obsolete::kMd5Size> digest =
+      brave::Md5ForDefaultProtocolHandler(bytes);
+  auto md5 = base::as_byte_span(digest).first<8u>();
 
   // The following loop effectively computes two checksums, scrambled like a
   // hash after every DWORD is added.

chromium_src/crypto/obsolete/md5.h

@@ -0,0 +1,28 @@
+/* Copyright (c) 2025 The Brave Authors. All rights reserved.
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+#ifndef BRAVE_CHROMIUM_SRC_CRYPTO_OBSOLETE_MD5_H_
+#define BRAVE_CHROMIUM_SRC_CRYPTO_OBSOLETE_MD5_H_
+
+// In order to continue using MD5 (which has now moved to //crypto/obsolete) for
+// our default protocol handler, we must mark our helper function as a friend of
+// Md5. This is a standard pattern used by upstream code that wishes to continue
+// using Md5.
+#define KnownAnswer                                                    \
+  KnownAnswer); friend std::array<uint8_t, crypto::obsolete::kMd5Size> \
+  brave::Md5ForDefaultProtocolHandler(base::span<const uint8_t> data
+
+#define BRAVE_CRYPTO_OBSOLETE_MD5                               \
+  namespace brave {                                             \
+  std::array<uint8_t, crypto::obsolete::kMd5Size>               \
+  Md5ForDefaultProtocolHandler(base::span<const uint8_t> data); \
+  }
+
+#include <crypto/obsolete/md5.h>  // IWYU pragma: export
+
+#undef BRAVE_CRYPTO_OBSOLETE_MD5
+#undef KnownAnswer
+
+#endif  // BRAVE_CHROMIUM_SRC_CRYPTO_OBSOLETE_MD5_H_

patches/crypto-obsolete-md5.h.patch

@@ -0,0 +1,12 @@
+diff --git a/crypto/obsolete/md5.h b/crypto/obsolete/md5.h
+index 3c8cc67a081f04b4526e2b0e5a4984fa0f73ff9c..7a463946d2613dc5928ee279bcca74d84ed380e7 100644
+--- a/crypto/obsolete/md5.h
++++ b/crypto/obsolete/md5.h
+@@ -152,6 +152,7 @@ namespace web_app::internals {
+ crypto::obsolete::Md5 MakeMd5HasherForWebAppShortcutIcon();
+ std::wstring Md5AsHexForUninstall(const std::wstring& data);
+ }
++BRAVE_CRYPTO_OBSOLETE_MD5
+ 
+ namespace crypto::obsolete {
+