Adds more customization options to the Chip widget (#11498)

* Adds more customization options to the Chip widget

Includes:
- Custom Tooltip message for the delete button;
- Custom background color for the chip
- Custom delete icon color
- Custom label text style

* Adds missing type annotations to tests and improves documentation.

* Tweaks labelStyle field documentation

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

@@ -19,7 +19,7 @@ const TextStyle _kLabelStyle = const TextStyle(
   fontSize: 13.0,
   fontWeight: FontWeight.w400,
   color: Colors.black87,
-  textBaseline: TextBaseline.alphabetic
+  textBaseline: TextBaseline.alphabetic,
 );
 
 /// A material design chip.
@@ -57,6 +57,10 @@ class Chip extends StatelessWidget {
     this.avatar,
     @required this.label,
     this.onDeleted,
+    this.labelStyle,
+    this.deleteButtonTooltipMessage,
+    this.backgroundColor,
+    this.deleteIconColor,
   }) : super(key: key);
 
   /// A widget to display prior to the chip's label.
@@ -74,6 +78,30 @@ class Chip extends StatelessWidget {
   /// The delete button is included in the chip only if this callback is non-null.
   final VoidCallback onDeleted;
 
+  /// The style to be applied to the chip's label.
+  ///
+  /// This only has effect on widgets that respect the [DefaultTextStyle],
+  /// such as [Text].
+  final TextStyle labelStyle;
+
+  /// Color to be used for the chip's background, the default being grey.
+  ///
+  /// This color is used as the background of the container that will hold the
+  /// widget's label.
+  final Color backgroundColor;
+
+  /// Color for delete icon, the default being black.
+  ///
+  /// This has no effect when [onDelete] is null since no delete icon will be
+  /// shown.
+  final Color deleteIconColor;
+
+  /// Message to be used for the chip delete button's tooltip.
+  ///
+  /// This has no effect when [onDelete] is null since no delete icon will be
+  /// shown.
+  final String deleteButtonTooltipMessage;
+
   @override
   Widget build(BuildContext context) {
     assert(debugCheckHasMaterial(context));
@@ -90,14 +118,14 @@ class Chip extends StatelessWidget {
           margin: const EdgeInsets.only(right: 8.0),
           width: _kAvatarDiamater,
           height: _kAvatarDiamater,
-          child: avatar
-        )
+          child: avatar,
+        ),
       ));
     }
 
     children.add(new DefaultTextStyle(
-      style: _kLabelStyle,
-      child: label
+      style: labelStyle ?? _kLabelStyle,
+      child: label,
     ));
 
     if (deletable) {
@@ -105,16 +133,16 @@ class Chip extends StatelessWidget {
       children.add(new GestureDetector(
         onTap: Feedback.wrapForTap(onDeleted, context),
         child: new Tooltip(
-          message: 'Delete "$label"',
+          message: deleteButtonTooltipMessage ?? 'Delete "$label"',
           child: new Container(
             padding: const EdgeInsets.symmetric(horizontal: 4.0),
-            child: const Icon(
+            child: new Icon(
               Icons.cancel,
               size: 18.0,
-              color: Colors.black54
-            )
-          )
-        )
+              color: deleteIconColor ?? Colors.black54,
+            ),
+          ),
+        ),
       ));
     }
 
@@ -124,14 +152,14 @@ class Chip extends StatelessWidget {
         height: _kChipHeight,
         padding: new EdgeInsets.only(left: leftPadding, right: rightPadding),
         decoration: new BoxDecoration(
-          color: Colors.grey.shade300,
-          borderRadius: new BorderRadius.circular(16.0)
+          color: backgroundColor ?? Colors.grey.shade300,
+          borderRadius: new BorderRadius.circular(16.0),
         ),
         child: new Row(
           children: children,
-          mainAxisSize: MainAxisSize.min
-        )
-      )
+          mainAxisSize: MainAxisSize.min,
+        ),
+      ),
     );
   }
 }

packages/flutter/test/material/chip_test.dart

@@ -10,34 +10,56 @@ import 'feedback_tester.dart';
 void main() {
   testWidgets('Chip control test', (WidgetTester tester) async {
     final FeedbackTester feedback = new FeedbackTester();
-    bool didDeleteChip = false;
+    final List<String> deletedChipLabels = <String>[];
     await tester.pumpWidget(
       new MaterialApp(
         home: new Material(
-          child: new Center(
-            child: new Chip(
-              avatar: const CircleAvatar(
-                child: const Text('C')
+          child: new Column(
+            children: <Widget>[
+              new Chip(
+                avatar: const CircleAvatar(
+                  child: const Text('A')
+                ),
+                label: const Text('Chip A'),
+                onDeleted: () {
+                  deletedChipLabels.add('A');
+                },
+                deleteButtonTooltipMessage: 'Delete chip A',
               ),
-              label: const Text('Chip'),
-              onDeleted: () {
-                didDeleteChip = true;
-              }
-            )
+              new Chip(
+                avatar: const CircleAvatar(
+                  child: const Text('B')
+                ),
+                label: const Text('Chip B'),
+                onDeleted: () {
+                  deletedChipLabels.add('B');
+                },
+                deleteButtonTooltipMessage: 'Delete chip B',
+              ),
+            ]
           )
         )
       )
     );
 
+    expect(tester.widget(find.byTooltip('Delete chip A')), isNotNull);
+    expect(tester.widget(find.byTooltip('Delete chip B')), isNotNull);
+
     expect(feedback.clickSoundCount, 0);
 
-    expect(didDeleteChip, isFalse);
-    await tester.tap(find.byType(Tooltip));
-    expect(didDeleteChip, isTrue);
+    expect(deletedChipLabels, isEmpty);
+    await tester.tap(find.byTooltip('Delete chip A'));
+    expect(deletedChipLabels, equals(<String>['A']));
 
     await tester.pumpAndSettle(const Duration(seconds: 1));
     expect(feedback.clickSoundCount, 1);
 
+    await tester.tap(find.byTooltip('Delete chip B'));
+    expect(deletedChipLabels, equals(<String>['A', 'B']));
+
+    await tester.pumpAndSettle(const Duration(seconds: 1));
+    expect(feedback.clickSoundCount, 2);
+
     feedback.dispose();
   });
 }