[plaster] Add an example using plaster to generate a patch file (#31132)

Add description
Add ignore-eol to align with nodejs updatePatches.js

patches/chrome-utility-BUILD.gn.patch

@@ -1,13 +1,12 @@
 diff --git a/chrome/utility/BUILD.gn b/chrome/utility/BUILD.gn
-index 88b6b588f581338a8873767e64d08dcf5333240c..9556d02ac2c9babde33d8e7837ce919b148ad459 100644
+index 88b6b588f581338a8873767e64d08dcf5333240c..3241c78ddc8d2a5bf32190d22cc6593fa73792db 100644
 --- a/chrome/utility/BUILD.gn
 +++ b/chrome/utility/BUILD.gn
-@@ -77,6 +77,8 @@ static_library("utility") {
-     "//ui/base:buildflags",
-   ]
- 
+@@ -268,6 +268,7 @@ static_library("utility") {
+   if (enable_on_device_translation) {
+     deps += [ "//components/services/on_device_translation:on_device_translation_service" ]
+   }
 +  import("//brave/utility/sources.gni") sources += brave_utility_sources deps += brave_utility_deps public_deps += brave_utility_public_deps
-+
-   if (is_win) {
-     deps += [
-       "//components/services/quarantine",
+ }
+ 
+ if (!is_android) {

rewrite/chrome/utility/BUILD.gn.toml

@@ -0,0 +1,10 @@
+# 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/.
+
+[[substitution]]
+description = 'Add brave/utility sources'
+re_pattern = '''(static_library\("utility"\) {[\s\S]*?)(^})'''
+re_flags = ['MULTILINE']
+replace = '''\1  import("//brave/utility/sources.gni") sources += brave_utility_sources deps += brave_utility_deps public_deps += brave_utility_public_deps\n\2'''

tools/cr/plaster.py

@@ -204,6 +204,7 @@ class PatchInfo:
                                               '--dst-prefix=b/',
                                               '--default-prefix',
                                               '--full-index',
+                                              '--ignore-space-at-eol',
                                               self.source,
                                               no_trim=True)
         return self.patch.save_if_changed(new_content=content, dry_run=dry_run)
@@ -256,12 +257,16 @@ class PlasterFile:
         contents = repository.chromium.read_file(info.source)
 
         for substitution in plaster_file.get('substitution'):
+            description = substitution.get('description')
             re_pattern = substitution.get('re_pattern')
             pattern = substitution.get('pattern')
             replace = substitution.get('replace')
             expected_count = substitution.get('count', 1)
             flags = substitution.get('re_flags', [])
 
+            if description is None:
+                raise ValueError(f'No description specified in {info.source}')
+
             if re_pattern is not None and pattern is not None:
                 raise ValueError(
                     f'Please specify either pattern or re_pattern '