Update the magic number for JPEG to just FF D8 FF. (#32076)

Author: Harry Terkelsen

lib/web_ui/lib/src/engine/canvaskit/image_web_codecs.dart

@@ -297,10 +297,7 @@ class ImageFileFormat {
     ImageFileFormat(<int?>[0x47, 0x49, 0x46, 0x38, 0x39, 0x61], 'image/gif'),
 
     // JPEG
-    ImageFileFormat(<int?>[0xFF, 0xD8, 0xFF, 0xDB], 'image/jpeg'),
-    ImageFileFormat(<int?>[0xFF, 0xD8, 0xFF, 0xE0, 0x00, 0x10, 0x4A, 0x46, 0x49, 0x46, 0x00, 0x01], 'image/jpeg'),
-    ImageFileFormat(<int?>[0xFF, 0xD8, 0xFF, 0xEE], 'image/jpeg'),
-    ImageFileFormat(<int?>[0xFF, 0xD8, 0xFF, 0xE1], 'image/jpeg'),
+    ImageFileFormat(<int?>[0xFF, 0xD8, 0xFF], 'image/jpeg'),
 
     // WebP
     ImageFileFormat(<int?>[0x52, 0x49, 0x46, 0x46, null, null, null, null, 0x57, 0x45, 0x42, 0x50], 'image/webp'),

lib/web_ui/test/canvaskit/image_golden_test.dart

@@ -529,6 +529,13 @@ void _testForImageCodecs({required bool useBrowserImageDecoder}) {
 
       await disposePlatformView(0);
     });
+
+    test('can detect JPEG from just magic number', () async {
+      expect(
+        detectContentType(
+          Uint8List.fromList(<int>[0xff, 0xd8, 0xff, 0xe2, 0x0c, 0x58, 0x49, 0x43, 0x43, 0x5f])),
+        'image/jpeg');
+    });
   });
 }