Adjust the IconButton constraint to match its size (#6226)

Fixes https://github.com/flutter/flutter/issues/5763

packages/flutter/lib/src/material/icon_button.dart

@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+import 'dart:math' as math;
+
 import 'package:flutter/widgets.dart';
 import 'package:meta/meta.dart';
 
@@ -126,7 +128,7 @@ class IconButton extends StatelessWidget {
         maxHeight: size,
         child: new ConstrainedBox(
           constraints: new BoxConstraints.loose(
-            const Size.square(InkSplash.defaultRadius * 2.0)
+            new Size.square(math.max(size, InkSplash.defaultRadius * 2.0))
           ),
           child: new Align(
             alignment: alignment,
@@ -150,7 +152,8 @@ class IconButton extends StatelessWidget {
     }
     return new InkResponse(
       onTap: onPressed,
-      child: result
+      child: result,
+      radius: math.max(size, InkSplash.defaultRadius),
     );
   }
 

packages/flutter/lib/src/material/ink_well.dart

@@ -36,7 +36,8 @@ class InkResponse extends StatefulWidget {
     this.onLongPress,
     this.onHighlightChanged,
     this.containedInkWell: false,
-    this.highlightShape: BoxShape.circle
+    this.highlightShape: BoxShape.circle,
+    this.radius,
   }) : super(key: key);
 
   /// The widget below this widget in the tree.
@@ -64,6 +65,9 @@ class InkResponse extends StatefulWidget {
   /// The shape (e.g., circle, rectangle) to use for the highlight drawn around this part of the material.
   final BoxShape highlightShape;
 
+  /// The radius of the ink splash.
+  final double radius;
+
   /// The rectangle to use for the highlight effect and for clipping
   /// the splash effects if [containedInkWell] is true.
   ///
@@ -138,6 +142,7 @@ class _InkResponseState<T extends InkResponse> extends State<T> {
       color: Theme.of(context).splashColor,
       containedInkWell: config.containedInkWell,
       rectCallback: config.containedInkWell ? rectCallback : null,
+      radius: config.radius,
       onRemoved: () {
         if (_splashes != null) {
           assert(_splashes.contains(splash));

packages/flutter/lib/src/material/material.dart

@@ -121,7 +121,8 @@ abstract class MaterialInkController {
     Color color,
     bool containedInkWell: false,
     RectCallback rectCallback,
-    VoidCallback onRemoved
+    VoidCallback onRemoved,
+    double radius,
   });
 
   /// Begin a highlight animation. If a rectCallback is given, then it
@@ -321,9 +322,9 @@ class _RenderInkFeatures extends RenderProxyBox implements MaterialInkController
     Color color,
     bool containedInkWell: false,
     RectCallback rectCallback,
-    VoidCallback onRemoved
+    VoidCallback onRemoved,
+    double radius,
   }) {
-    double radius;
     RectCallback clipCallback;
     if (containedInkWell) {
       Size size;
@@ -334,10 +335,10 @@ class _RenderInkFeatures extends RenderProxyBox implements MaterialInkController
         size = referenceBox.size;
         clipCallback = () => Point.origin & referenceBox.size;
       }
-      radius = _getSplashTargetSize(size, position);
+      radius ??= _getSplashTargetSize(size, position);
     } else {
       assert(rectCallback == null);
-      radius = InkSplash.defaultRadius;
+      radius ??= InkSplash.defaultRadius;
     }
     _InkSplash splash = new _InkSplash(
       controller: this,

packages/flutter/test/material/icon_button_test.dart

@@ -7,21 +7,24 @@ import 'package:flutter_test/flutter_test.dart';
 
 void main() {
   testWidgets('IconButton test constrained size', (WidgetTester tester) async {
+    const double kIconSize = 80.0;
+
     await tester.pumpWidget(
       new Material(
         child: new Center(
           child: new IconButton(
             padding: EdgeInsets.zero,
             onPressed: () {},
-            icon: new Icon(Icons.ac_unit)
+            icon: new Icon(Icons.ac_unit),
+            size: kIconSize,
           )
         )
       )
     );
 
     RenderBox box = tester.renderObject(find.byType(IconButton));
-    expect(box.size.width, equals(InkSplash.defaultRadius * 2.0));
-    expect(box.size.height, equals(InkSplash.defaultRadius * 2.0));
+    expect(box.size.width, equals(kIconSize));
+    expect(box.size.height, equals(kIconSize));
   });
 
   testWidgets('IconButton AppBar size', (WidgetTester tester) async {
@@ -32,7 +35,7 @@ void main() {
             new IconButton(
               padding: EdgeInsets.zero,
               onPressed: () {},
-              icon: new Icon(Icons.ac_unit)
+              icon: new Icon(Icons.ac_unit),
             )
           ]
         )