ImageFilter default tile mode automatic selection breaking change notice

src/content/release/breaking-changes/image-filter-blur-tilemode.md

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+---
+title: ImageFilter.blur default tile mode automatic selection.
+description: >-
+  If a tile mode wasn't specified in the constructor, ImageFilter.blur will
+  select one based on the rendering context.
+---
+
+## Summary
+
+  The `ui.ImageFilter.blur`'s default tile mode is now automatically selected
+  by the backend. Previously `TileMode.clamp` was used unless a different tile
+  mode was specified. Passing a value of `null` to the filter's constructor
+  specifies automatic selection.
+
+## Background
+
+  `ImageFilter`'s _tile mode_ specifies what happens to edge pixels for the
+  applied filter. There are four options, `TileMode.clamp` (the previous
+  default), `Tilemode.repeated`, `TileMode.mirror`, and `TileMode.decal`.
+  Previously, `ImageFilter` defaulted to `clamp` mode if the
+  behavior wasn't specified, which sometimes surprised developers
+  as it didn't always match expectations.
+
+  As of this change, the filter automatically selects the following tile modes
+  based on context:
+
+  * `decal` with save layers and when applied to individual draws.
+  * `mirror` with backdrop filters.
+  * `clamp` for drawImage.
+
+## Migration guide
+
+  Only image filters that don't specify an explicit tile mode are
+  impacted by this change. In these cases, you can specify an explicit tile
+  mode to retain the prior behavior. However, we believe the automatic
+  selection of behavior will be a superior choice in most cases.
+
+Code before migration:
+
+```dart
+var filter = ui.ImageFilter.blur(sigmaX: 4, sigmaY: 4);
+```
+
+Code after migration:
+
+```dart
+// Set tile mode to old default.
+var filter = ui.ImageFilter.blur(sigmaX: 4, sigmaY: 4, tileMode: TileMode.clamp);
+```
+
+## Timeline
+
+Landed in version: xxx<br>
+In stable release: Not yet
+
+## References
+
+{% include docs/main-api.md %}
+
+API documentation:
+
+* [`ImageFilter`][]
+* [`TileMode`][]
+
+Relevant issues:
+
+* [Issue #154935][]
+* [Issue #110318][]
+* [Issue #157693][]
+
+Relevant PRs:
+
+* [Change default TileMode for blur ImageFilter objects to null][]
+
+
+[`ImageFilter`]: https://api.flutter.dev/flutter/dart-ui/ImageFilter-class.html
+[`ImageFilter.blur`]: https://api.flutter.dev/flutter/dart-ui/ImageFilter/ImageFilter.blur.html
+[`TileMode`]: https://api.flutter.dev/flutter/dart-ui/TileMode.html
+[Issue #154935]: https://github.com/flutter/flutter/issues/154935
+[Issue #110318]: https://github.com/flutter/flutter/issues/110318
+[Issue #157693]: https://github.com/flutter/flutter/issues/157693
+[Change default TileMode for blur ImageFilter objects to null]: https://github.com/flutter/engine/pull/55552