[web] fix io_patch files to match nullability of encoding parameters

Fixes #46726

Change-Id: Idf9b8b2fcfd3eb59dd25a84ade0ad2a36fe7648d
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/208145
Reviewed-by: Mark Zhou <markzipan@google.com>
Commit-Queue: Sigmund Cherem <sigmund@google.com>
diff --git a/sdk/lib/_internal/js_dev_runtime/patch/io_patch.dart b/sdk/lib/_internal/js_dev_runtime/patch/io_patch.dart
index 041dfd5..882f10c 100644
--- a/sdk/lib/_internal/js_dev_runtime/patch/io_patch.dart
+++ b/sdk/lib/_internal/js_dev_runtime/patch/io_patch.dart
@@ -364,8 +364,8 @@
       Map<String, String>? environment,
       bool includeParentEnvironment = true,
       bool runInShell = false,
-      Encoding stdoutEncoding = systemEncoding,
-      Encoding stderrEncoding = systemEncoding}) {
+      Encoding? stdoutEncoding = systemEncoding,
+      Encoding? stderrEncoding = systemEncoding}) {
     throw UnsupportedError("Process.run");
   }
 
@@ -375,8 +375,8 @@
       Map<String, String>? environment,
       bool includeParentEnvironment = true,
       bool runInShell = false,
-      Encoding stdoutEncoding = systemEncoding,
-      Encoding stderrEncoding = systemEncoding}) {
+      Encoding? stdoutEncoding = systemEncoding,
+      Encoding? stderrEncoding = systemEncoding}) {
     throw UnsupportedError("Process.runSync");
   }
 
diff --git a/sdk/lib/_internal/js_runtime/lib/io_patch.dart b/sdk/lib/_internal/js_runtime/lib/io_patch.dart
index 77a2530..2ee566b 100644
--- a/sdk/lib/_internal/js_runtime/lib/io_patch.dart
+++ b/sdk/lib/_internal/js_runtime/lib/io_patch.dart
@@ -364,8 +364,8 @@
       Map<String, String>? environment,
       bool includeParentEnvironment: true,
       bool runInShell: false,
-      Encoding stdoutEncoding: systemEncoding,
-      Encoding stderrEncoding: systemEncoding}) {
+      Encoding? stdoutEncoding: systemEncoding,
+      Encoding? stderrEncoding: systemEncoding}) {
     throw new UnsupportedError("Process.run");
   }
 
@@ -375,8 +375,8 @@
       Map<String, String>? environment,
       bool includeParentEnvironment: true,
       bool runInShell: false,
-      Encoding stdoutEncoding: systemEncoding,
-      Encoding stderrEncoding: systemEncoding}) {
+      Encoding? stdoutEncoding: systemEncoding,
+      Encoding? stderrEncoding: systemEncoding}) {
     throw new UnsupportedError("Process.runSync");
   }