Add a warning about Icon.size to IconButton (#91051)
diff --git a/packages/flutter/lib/src/material/icon_button.dart b/packages/flutter/lib/src/material/icon_button.dart
index d3c65a6..dd8ec4d 100644
--- a/packages/flutter/lib/src/material/icon_button.dart
+++ b/packages/flutter/lib/src/material/icon_button.dart
@@ -49,6 +49,26 @@
/// ** See code in examples/api/lib/material/icon_button/icon_button.0.dart **
/// {@end-tool}
///
+/// ### Icon sizes
+///
+/// When creating an icon button with an [Icon], do not override the
+/// icon's size with its [Icon.size] parameter, use the icon button's
+/// [iconSize] parameter instead. For example do this:
+///
+/// ```dart
+/// IconButton(iconSize: 72, icon: Icon(Icons.favorite), ...)
+/// ```
+///
+/// Avoid doing this:
+///
+/// ```dart
+/// IconButton(icon: Icon(Icons.favorite, size: 72), ...)
+/// ```
+///
+/// If you do, the button's size will be based on the default icon
+/// size, not 72, which may produce unexpected layouts and clipping
+/// issues.
+///
/// ### Adding a filled background
///
/// Icon buttons don't support specifying a background color or other
