[framework] load files through ImmutableBuffer.fromFilePath (if exact file type) (#112892)

Update FileImage to use the new ImmutableBuffer.fromFilePath constructor to avoid loading bytes through the Dart heap. As a side effect, tis fixes #112881 which prevents dart:io from opening a file larger than INT_MAX bytes on windows.

For files that are not exactly a dart:io file, we still use the old method of calling loadBytes() in order to not make this a breaking change.

packages/flutter/lib/src/painting/image_provider.dart

@@ -991,17 +991,23 @@ class FileImage extends ImageProvider<FileImage> {
   Future<ui.Codec> _loadAsync(FileImage key, DecoderBufferCallback? decode, DecoderCallback? decodeDeprecated) async {
     assert(key == this);
 
-    final Uint8List bytes = await file.readAsBytes();
-    if (bytes.lengthInBytes == 0) {
+    // TODO(jonahwilliams): making this sync caused test failures that seem to
+    // indicate that we can fail to call evict unless at least one await has
+    // occurred in the test.
+    // https://github.com/flutter/flutter/issues/113044
+    final int lengthInBytes = await file.length();
+    if (lengthInBytes == 0) {
       // The file may become available later.
       PaintingBinding.instance.imageCache.evict(key);
       throw StateError('$file is empty and cannot be loaded as an image.');
     }
-
     if (decode != null) {
-      return decode(await ui.ImmutableBuffer.fromUint8List(bytes));
+      if (file.runtimeType == File) {
+        return decode(await ui.ImmutableBuffer.fromFilePath(file.path));
+      }
+      return decode(await ui.ImmutableBuffer.fromUint8List(await file.readAsBytes()));
     }
-    return decodeDeprecated!(bytes);
+    return decodeDeprecated!(await file.readAsBytes());
   }
 
   @override

packages/flutter/test/painting/image_provider_test.dart

@@ -136,6 +136,29 @@ void main() {
 
     expect(completer.debugLabel, 'MemoryImage(${describeIdentity(bytes)}) - Resized(40×40)');
   });
+
+  test('File image throws error when given a real but non-image file', () async {
+    final Completer<Exception> error = Completer<Exception>();
+    FlutterError.onError = (FlutterErrorDetails details) {
+      error.complete(details.exception as Exception);
+    };
+    final FileImage provider = FileImage(File('pubspec.yaml'));
+
+    expect(imageCache.statusForKey(provider).untracked, true);
+    expect(imageCache.pendingImageCount, 0);
+
+    provider.resolve(ImageConfiguration.empty);
+
+    expect(imageCache.statusForKey(provider).pending, true);
+    expect(imageCache.pendingImageCount, 1);
+
+    expect(await error.future, isException
+      .having((Exception exception) => exception.toString(), 'toString', contains('Invalid image data')));
+
+    // Invalid images are marked as pending so that we do not attempt to reload them.
+    expect(imageCache.statusForKey(provider).untracked, false);
+    expect(imageCache.pendingImageCount, 1);
+  }, skip: kIsWeb); // [intended] The web cannot load files.
 }
 
 class FakeCodec implements Codec {