Fix ExtendedFloatingActionButton width (#16168)

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

@@ -254,14 +254,13 @@ class _FloatingActionButtonState extends State<FloatingActionButton> {
     }
 
     if (widget.tooltip != null) {
+      final Widget tooltip = new Tooltip(
+        message: widget.tooltip,
+        child: result,
+      );
       // The long-pressable area for the tooltip should always be as big as
       // the tooltip even if there is no child.
-      result = new SizedBox.expand(
-        child: new Tooltip(
-          message: widget.tooltip,
-          child: result,
-        ),
-      );
+      result = widget.child != null ? tooltip : new SizedBox.expand(child: tooltip);
     }
 
     result = new RawMaterialButton(

packages/flutter/test/material/floating_action_button_test.dart

@@ -91,7 +91,10 @@ void main() {
       new MaterialApp(
         home: new Scaffold(
           floatingActionButton: new FloatingActionButton.extended(
-            label: const Text('label'),
+            label: const SizedBox(
+              width: 100.0,
+              child: const Text('label'),
+            ),
             icon: const Icon(Icons.android),
             onPressed: null,
           ),
@@ -107,6 +110,7 @@ void main() {
     // Verify that the widget's height is 48 and that its internal
     /// horizontal layout is: 16 icon 8 label 20
     expect(tester.getSize(fabFinder).height, 48.0);
+
     final double fabLeft = tester.getTopLeft(fabFinder).dx;
     final double fabRight = tester.getTopRight(fabFinder).dx;
     final double iconLeft = tester.getTopLeft(find.byType(Icon)).dx;
@@ -116,6 +120,12 @@ void main() {
     expect(iconLeft - fabLeft, 16.0);
     expect(labelLeft - iconRight, 8.0);
     expect(fabRight - labelRight, 20.0);
+
+    // The overall width of the button is:
+    // 168 = 16 + 24(icon) + 8 + 100(label) + 20
+    expect(tester.getSize(find.byType(Icon)).width, 24.0);
+    expect(tester.getSize(find.text('label')).width, 100.0);
+    expect(tester.getSize(fabFinder).width, 168);
   });
 
   testWidgets('Floating Action Button heroTag', (WidgetTester tester) async {