[dart2wasm] Ensure we never emit string import names that are longer than 100_000 bytes

D8 currently allows longer import names bot JSShell and JSC do
issue a validation error if the name is larger than 100_000.

This fixes e.g. StarryStrings benchmarks on JSC/JSShell

TEST=tests/web/wasm/long_string_import_test.dart

Change-Id: I93df5d0e3014f6157750511fe486677e9b9413d7
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/450922
Reviewed-by: Ömer Ağacan <omersa@google.com>
Commit-Queue: Martin Kustermann <kustermann@google.com>

pkg/dart2wasm/lib/translator.dart

@@ -2,6 +2,8 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
+import 'dart:convert';
+
 import 'package:kernel/ast.dart';
 import 'package:kernel/class_hierarchy.dart'
     show ClassHierarchy, ClassHierarchySubtypes, ClosedWorldClassHierarchy;
@@ -1866,7 +1868,14 @@ class Translator with KernelNodes {
       return false;
     }
 
-    if (hasUnpairedSurrogate(s)) {
+    // Maximum length in bytes of an import name (JSC & JSShell will issue a
+    // wasm validation error if we import names larger than this).
+    const maxStringBytes = 100_000;
+    // A code unit of Dart string can take up max 3 bytes, we use it as first
+    // condition to avoid `utf8.encode()` in most situations.
+    final stringInBytesIsToLarge = (s.length * 3) > maxStringBytes &&
+        utf8.encode(s).length > maxStringBytes;
+    if (hasUnpairedSurrogate(s) || stringInBytesIsToLarge) {
       // Unpaired surrogates can't be encoded as UTF-8, import them from JS
       // runtime.
       final i = internalizedStringsForJSRuntime.length;

pkg/dart2wasm/pubspec.yaml

@@ -2,7 +2,7 @@ name: dart2wasm
 # This package is not intended for consumption on pub.dev. DO NOT publish.
 publish_to: none
 environment:
-  sdk: ^3.5.0
+  sdk: ^3.6.0
 
 resolution: workspace