Fix the output of the CDN test. (#148730)

This test was outputting the "success" string multiple times, which is probably causing the harness to kill the app halfway through its cycle. I suspect this is causing some of the flakiness we've seen of this test. Instead, we should just output the string at the very end of the test, right before the app is done.

dev/integration_tests/web/lib/framework_stack_trace.dart

@@ -35,14 +35,14 @@ Future<void> main() async {
     output.writeln('--- TEST FAILED ---');
   }
 
-  print(output);
-  web.window.fetch(
+  await web.window.fetch(
     '/test-result'.toJS,
     web.RequestInit(
       method: 'POST',
       body: '$output'.toJS,
     )
-  );
+  ).toDart;
+  print(output);
 }
 
 bool _errorMessageFormattedCorrectly(String errorMessage) {

dev/integration_tests/web/lib/sound_mode.dart

@@ -9,7 +9,7 @@ import 'dart:js_interop';
 import 'package:web/web.dart' as web;
 
 // Verify that web applications can be run in sound mode.
-void main() {
+void main() async {
   const bool isWeak = <int?>[] is List<int>;
   String output;
   if (isWeak) {
@@ -17,12 +17,12 @@ void main() {
   } else {
     output = '--- TEST SUCCEEDED ---';
   }
-  print(output);
-  web.window.fetch(
+  await web.window.fetch(
     '/test-result'.toJS,
     web.RequestInit(
       method: 'POST',
       body: output.toJS,
     )
-  );
+  ).toDart;
+  print(output);
 }

dev/integration_tests/web/lib/stack_trace.dart

@@ -66,7 +66,7 @@ const List<StackFrame> expectedDebugStackFrames = <StackFrame>[
 /// Tests that we do not crash while parsing Web stack traces.
 ///
 /// This test is run in debug, profile, and release modes.
-void main() {
+void main() async {
   final StringBuffer output = StringBuffer();
   try {
     try {
@@ -97,14 +97,14 @@ void main() {
     output.writeln(unexpectedStackTrace);
     output.writeln('--- TEST FAILED ---');
   }
-  print(output);
-  web.window.fetch(
+  await web.window.fetch(
     '/test-result'.toJS,
     web.RequestInit(
       method: 'POST',
       body: '$output'.toJS,
     )
-  );
+  ).toDart;
+  print(output);
 }
 
 @noInline

dev/integration_tests/web/lib/web_define_loading.dart

@@ -12,17 +12,16 @@ Future<void> main() async {
     String.fromEnvironment('test.valueB');
   if (combined == 'Example,AValue') {
     output.write('--- TEST SUCCEEDED ---');
-    print('--- TEST SUCCEEDED ---');
   } else {
     output.write('--- TEST FAILED ---');
-    print('--- TEST FAILED ---');
   }
 
-  web.window.fetch(
+  await web.window.fetch(
     '/test-result'.toJS,
     web.RequestInit(
       method: 'POST',
       body: '$output'.toJS,
     )
-  );
+  ).toDart;
+  print(output);
 }

dev/integration_tests/web/lib/web_resources_cdn_test.dart

@@ -6,12 +6,19 @@ import 'dart:js_interop';
 
 import 'package:web/web.dart' as web;
 
-// Attempt to load CanvasKit resources hosted on gstatic.
 Future<void> main() async {
+  if (await testFetchResources()) {
+    print('--- TEST SUCCEEDED ---');
+  } else {
+    print('--- TEST FAILED ---');
+  }
+}
+
+// Attempt to load CanvasKit resources hosted on gstatic.
+Future<bool> testFetchResources() async {
   const String engineVersion = String.fromEnvironment('TEST_FLUTTER_ENGINE_VERSION');
   if (engineVersion.isEmpty) {
-    print('--- TEST FAILED ---');
-    return;
+    return false;
   }
   try {
     final web.Response response = await web.window.fetch(
@@ -20,14 +27,12 @@ Future<void> main() async {
         method: 'GET',
       ),
     ).toDart;
-    if (response.ok) {
-      print('--- TEST SUCCEEDED ---');
-    } else {
-      print('--- TEST FAILED ---');
+    if (!response.ok) {
+      return false;
     }
   } catch (err) {
     print(err);
-    print('--- TEST FAILED ---');
+    return false;
   }
   try {
     final web.Response response = await web.window.fetch(
@@ -36,13 +41,12 @@ Future<void> main() async {
         method: 'GET',
       )
     ).toDart;
-    if (response.ok) {
-      print('--- TEST SUCCEEDED ---');
-    } else {
-      print('--- TEST FAILED ---');
+    if (!response.ok) {
+      return false;
     }
   } catch (err) {
     print(err);
-    print('--- TEST FAILED ---');
+    return false;
   }
+  return true;
 }