Migrated away from UnmodifiableUint8ListView (flutter/engine#47276)

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engine/src/flutter/lib/ui/fixtures/ui_test.dart

@@ -273,9 +273,16 @@ void platformMessagePortResponseTest() async {
 @pragma('vm:entry-point')
 void platformMessageResponseTest() {
   _callPlatformMessageResponseDart((ByteData? result) {
-    if (result is UnmodifiableByteDataView &&
-        result.lengthInBytes == 100) {
-      _finishCallResponse(true);
+    if (result is ByteData && result.lengthInBytes == 100) {
+      int value = result.getInt8(0);
+      bool didThrowOnModify = false;
+      try {
+        result.setInt8(0, value);
+      } catch (e) {
+        didThrowOnModify = true;
+      }
+      // This should be a read only buffer.
+      _finishCallResponse(didThrowOnModify);
     } else {
       _finishCallResponse(false);
     }

engine/src/flutter/lib/ui/platform_dispatcher.dart

@@ -73,7 +73,7 @@ const String _kFlutterKeyDataChannel = 'flutter/keydata';
 
 @pragma('vm:entry-point')
 ByteData? _wrapUnmodifiableByteData(ByteData? byteData) =>
-    byteData == null ? null : UnmodifiableByteDataView(byteData);
+    byteData?.asUnmodifiableView();
 
 /// A token that represents a root isolate.
 class RootIsolateToken {

engine/src/flutter/shell/platform/fuchsia/dart-pkg/zircon/test/zircon_tests.dart

@@ -589,7 +589,7 @@ void main() {
       expect(fileResult.status, equals(ZX.OK));
       MapResult mapResult = System.vmoMap(fileResult.handle);
       expect(mapResult.status, equals(ZX.OK));
-      Uint8List fileData = UnmodifiableUint8ListView(mapResult.data);
+      Uint8List fileData = mapResult.data.asUnmodifiableView();
       String fileString = utf8.decode(fileData.sublist(0, fileResult.numBytes));
       expect(fileString, equals(fuchsia));
     });
@@ -610,7 +610,7 @@ void main() {
       // Read from the duplicate.
       MapResult mapResult = System.vmoMap(duplicate);
       expect(mapResult.status, equals(ZX.OK));
-      Uint8List vmoData = UnmodifiableUint8ListView(mapResult.data);
+      Uint8List vmoData = mapResult.data.asUnmodifiableView();
       String vmoString = utf8.decode(vmoData.sublist(0, data.length));
       expect(vmoString, equals(fuchsia));
     });