[web] Update felt to use generated JS runtime for Dart2Wasm. (#38786)

Author: joshualitt

lib/web_ui/dev/steps/compile_tests_step.dart

@@ -46,7 +46,6 @@ class CompileTestsStep implements PipelineStep {
     await environment.webUiBuildDir.create();
     if (isWasm) {
       await copyDart2WasmTestScript();
-      await copyDart2WasmRuntime();
     }
     await copyCanvasKitFiles(useLocalCanvasKit: useLocalCanvasKit);
     await buildHostPage();
@@ -129,20 +128,6 @@ Future<void> copySkiaTestImages() async {
   }
 }
 
-Future<void> copyDart2WasmRuntime() async {
-  final io.File sourceFile = io.File(pathlib.join(
-    environment.dartSdkDir.path,
-    'bin',
-    'dart2wasm_runtime.mjs',
-  ));
-  final io.Directory targetDir = io.Directory(pathlib.join(
-    environment.webUiBuildDir.path,
-    'dart2wasm_runtime.mjs',
-  ));
-
-  await sourceFile.copy(targetDir.path);
-}
-
 Future<void> copyDart2WasmTestScript() async {
   final io.File sourceFile = io.File(pathlib.join(
     environment.webUiDevDir.path,

lib/web_ui/dev/test_dart2wasm.js

@@ -54,8 +54,9 @@ window.onload = async function () {
   let dart2wasm_runtime;
   let moduleInstance;
   try {
-    dart2wasm_runtime = await import('./dart2wasm_runtime.mjs');
-    const dartModulePromise = WebAssembly.compileStreaming(fetch(link.href + ".browser_test.dart.wasm"));
+    let baseName = link.href + '.browser_test.dart';
+    dart2wasm_runtime = await import(baseName + '.mjs');
+    const dartModulePromise = WebAssembly.compileStreaming(fetch(baseName + '.wasm'));
     moduleInstance = await dart2wasm_runtime.instantiate(dartModulePromise, {});
   } catch (exception) {
     const message = `Failed to fetch and instantiate wasm module: ${exception}`;