prefer const constructor (#7118)

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

@@ -265,10 +265,10 @@ class AboutDialog extends StatelessWidget {
     final Widget icon = applicationIcon ?? _defaultApplicationIcon(context);
     List<Widget> body = <Widget>[];
     if (icon != null)
-      body.add(new IconTheme(data: new IconThemeData(size: 48.0), child: icon));
+      body.add(new IconTheme(data: const IconThemeData(size: 48.0), child: icon));
     body.add(new Expanded(
       child: new Padding(
-        padding: new EdgeInsets.symmetric(horizontal: 24.0),
+        padding: const EdgeInsets.symmetric(horizontal: 24.0),
         child: new BlockBody(
           children: <Widget>[
             new Text(name, style: Theme.of(context).textTheme.headline),
@@ -381,15 +381,15 @@ class _LicensePageState extends State<LicensePage> {
     await for (LicenseEntry license in LicenseRegistry.licenses) {
       setState(() {
         _licenses.add(new Padding(
-          padding: new EdgeInsets.symmetric(vertical: 18.0),
+          padding: const EdgeInsets.symmetric(vertical: 18.0),
           child: new Text(
             '🍀‬', // That's U+1F340. Could also use U+2766 (❦) if U+1F340 doesn't work everywhere.
             textAlign: TextAlign.center
           )
         ));
         _licenses.add(new Container(
-          decoration: new BoxDecoration(
+          decoration: const BoxDecoration(
-            border: new Border(bottom: new BorderSide(width: 0.0))
+            border: const Border(bottom: const BorderSide(width: 0.0))
           ),
           child: new Text(
             license.packages.join(', '),
@@ -400,7 +400,7 @@ class _LicensePageState extends State<LicensePage> {
         for (LicenseParagraph paragraph in license.paragraphs) {
           if (paragraph.indent == LicenseParagraph.centeredIndent) {
             _licenses.add(new Padding(
-              padding: new EdgeInsets.only(top: 16.0),
+              padding: const EdgeInsets.only(top: 16.0),
               child: new Text(
                 paragraph.text,
                 style: new TextStyle(fontWeight: FontWeight.bold),
@@ -438,7 +438,7 @@ class _LicensePageState extends State<LicensePage> {
     contents.addAll(_licenses);
     if (!_loaded) {
       contents.add(new Padding(
-        padding: new EdgeInsets.symmetric(vertical: 24.0),
+        padding: const EdgeInsets.symmetric(vertical: 24.0),
         child: new Center(
           child: new CircularProgressIndicator()
         )
@@ -452,7 +452,7 @@ class _LicensePageState extends State<LicensePage> {
         style: Theme.of(context).textTheme.caption,
         child: new Scrollbar(
           child: new LazyBlock(
-            padding: new EdgeInsets.symmetric(horizontal: 8.0, vertical: 12.0),
+            padding: const EdgeInsets.symmetric(horizontal: 8.0, vertical: 12.0),
             delegate: new LazyBlockChildren(
               children: contents
             )

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

@@ -397,7 +397,7 @@ class DataTable extends StatelessWidget {
         down: sorted ? ascending : null,
         duration: _kSortArrowAnimationDuration
       );
-      final Widget arrowPadding = new SizedBox(width: _kSortArrowPadding);
+      final Widget arrowPadding = const SizedBox(width: _kSortArrowPadding);
       label = new Row(
         children: numeric ? <Widget>[ arrow, arrowPadding, label ]
                           : <Widget>[ label, arrowPadding, arrow ]

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

@@ -52,9 +52,9 @@ class Dialog extends StatelessWidget {
   Widget build(BuildContext context) {
     return new Center(
       child: new Container(
-        margin: new EdgeInsets.symmetric(horizontal: 40.0, vertical: 24.0),
+        margin: const EdgeInsets.symmetric(horizontal: 40.0, vertical: 24.0),
         child: new ConstrainedBox(
-          constraints: new BoxConstraints(minWidth: 280.0),
+          constraints: const BoxConstraints(minWidth: 280.0),
           child: new Material(
             elevation: 24,
             color: _getColor(context),

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

@@ -154,8 +154,8 @@ class ExpansionPanelList extends StatelessWidget {
               new AnimatedCrossFade(
                 firstChild: new Container(height: 0.0),
                 secondChild: children[i].body,
-                firstCurve: new Interval(0.0, 0.6, curve: Curves.fastOutSlowIn),
+                firstCurve: const Interval(0.0, 0.6, curve: Curves.fastOutSlowIn),
-                secondCurve: new Interval(0.4, 1.0, curve: Curves.fastOutSlowIn),
+                secondCurve: const Interval(0.4, 1.0, curve: Curves.fastOutSlowIn),
                 sizeCurve: Curves.fastOutSlowIn,
                 crossFadeState: _isChildExpanded(i) ? CrossFadeState.showSecond : CrossFadeState.showFirst,
                 duration: animationDuration,

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

@@ -294,7 +294,7 @@ class PaginatedDataTableState extends State<PaginatedDataTable> {
         config.actions.map/*<Widget>*/((Widget widget) {
           return new Padding(
             // 8.0 is the default padding of an icon button
-            padding: new EdgeInsets.only(left: 24.0 - 8.0 * 2.0),
+            padding: const EdgeInsets.only(left: 24.0 - 8.0 * 2.0),
             child: widget
           );
         }).toList()
@@ -363,7 +363,7 @@ class PaginatedDataTableState extends State<PaginatedDataTable> {
                                          : themeData.textTheme.title.copyWith(fontWeight: FontWeight.w400),
             child: new IconTheme.merge(
               context: context,
-              data: new IconThemeData(
+              data: const IconThemeData(
                 opacity: 0.54
               ),
               child: new ButtonTheme.bar(
@@ -399,7 +399,7 @@ class PaginatedDataTableState extends State<PaginatedDataTable> {
             style: footerTextStyle,
             child: new IconTheme.merge(
               context: context,
-              data: new IconThemeData(
+              data: const IconThemeData(
                 opacity: 0.54
               ),
               child: new Container(

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

@@ -285,12 +285,12 @@ class _PopupMenu<T> extends StatelessWidget {
       ));
     }
 
-    final CurveTween opacity = new CurveTween(curve: new Interval(0.0, 1.0 / 3.0));
+    final CurveTween opacity = new CurveTween(curve: const Interval(0.0, 1.0 / 3.0));
     final CurveTween width = new CurveTween(curve: new Interval(0.0, unit));
     final CurveTween height = new CurveTween(curve: new Interval(0.0, unit * route.items.length));
 
     Widget child = new ConstrainedBox(
-      constraints: new BoxConstraints(
+      constraints: const BoxConstraints(
         minWidth: _kMenuMinWidth,
         maxWidth: _kMenuMaxWidth
       ),
@@ -388,7 +388,7 @@ class _PopupMenuRoute<T> extends PopupRoute<T> {
     return new CurvedAnimation(
       parent: super.createAnimation(),
       curve: Curves.linear,
-      reverseCurve: new Interval(0.0, _kMenuCloseIntervalEnd)
+      reverseCurve: const Interval(0.0, _kMenuCloseIntervalEnd)
     );
   }
 

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

@@ -168,7 +168,7 @@ class _LinearProgressIndicatorState extends State<LinearProgressIndicator> with
 
   Widget _buildIndicator(BuildContext context, double animationValue) {
     return new Container(
-      constraints: new BoxConstraints.tightFor(
+      constraints: const BoxConstraints.tightFor(
         width: double.INFINITY,
         height: _kLinearProgressIndicatorHeight
       ),
@@ -296,20 +296,20 @@ class CircularProgressIndicator extends ProgressIndicator {
 
 // Tweens used by circular progress indicator
 final Animatable<double> _kStrokeHeadTween = new CurveTween(
-  curve: new Interval(0.0, 0.5, curve: Curves.fastOutSlowIn)
+  curve: const Interval(0.0, 0.5, curve: Curves.fastOutSlowIn)
 ).chain(new CurveTween(
-  curve: new SawTooth(5)
+  curve: const SawTooth(5)
 ));
 
 final Animatable<double> _kStrokeTailTween = new CurveTween(
-  curve: new Interval(0.5, 1.0, curve: Curves.fastOutSlowIn)
+  curve: const Interval(0.5, 1.0, curve: Curves.fastOutSlowIn)
 ).chain(new CurveTween(
-  curve: new SawTooth(5)
+  curve: const SawTooth(5)
 ));
 
 final Animatable<int> _kStepTween = new StepTween(begin: 0, end: 5);
 
-final Animatable<double> _kRotationTween = new CurveTween(curve: new SawTooth(5));
+final Animatable<double> _kRotationTween = new CurveTween(curve: const SawTooth(5));
 
 class _CircularProgressIndicatorState extends State<CircularProgressIndicator> with SingleTickerProviderStateMixin {
   AnimationController _controller;
@@ -331,7 +331,7 @@ class _CircularProgressIndicatorState extends State<CircularProgressIndicator> w
 
   Widget _buildIndicator(BuildContext context, double headValue, double tailValue, int stepValue, double rotationValue) {
     return new Container(
-      constraints: new BoxConstraints(
+      constraints: const BoxConstraints(
         minWidth: _kMinCircularProgressIndicatorSize,
         minHeight: _kMinCircularProgressIndicatorSize,
       ),

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

@@ -357,7 +357,7 @@ class RefreshIndicatorState extends State<RefreshIndicator> with TickerProviderS
     )
     .animate(new CurvedAnimation(
       parent: _sizeController,
-      curve: new Interval(0.0, 1.0 / _kDragSizeFactorLimit)
+      curve: const Interval(0.0, 1.0 / _kDragSizeFactorLimit)
     ));
 
     return new Listener(

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

@@ -310,8 +310,8 @@ class _StepperState extends State<Stepper> with TickerProviderStateMixin {
       return new AnimatedCrossFade(
         firstChild: _buildCircle(index, true),
         secondChild: _buildTriangle(index, true),
-        firstCurve: new Interval(0.0, 0.6, curve: Curves.fastOutSlowIn),
+        firstCurve: const Interval(0.0, 0.6, curve: Curves.fastOutSlowIn),
-        secondCurve: new Interval(0.4, 1.0, curve: Curves.fastOutSlowIn),
+        secondCurve: const Interval(0.4, 1.0, curve: Curves.fastOutSlowIn),
         sizeCurve: Curves.fastOutSlowIn,
         crossFadeState: config.steps[index].state == StepState.error ? CrossFadeState.showSecond : CrossFadeState.showFirst,
         duration: kThemeAnimationDuration,
@@ -503,8 +503,8 @@ class _StepperState extends State<Stepper> with TickerProviderStateMixin {
               ]
             )
           ),
-          firstCurve: new Interval(0.0, 0.6, curve: Curves.fastOutSlowIn),
+          firstCurve: const Interval(0.0, 0.6, curve: Curves.fastOutSlowIn),
-          secondCurve: new Interval(0.4, 1.0, curve: Curves.fastOutSlowIn),
+          secondCurve: const Interval(0.4, 1.0, curve: Curves.fastOutSlowIn),
           sizeCurve: Curves.fastOutSlowIn,
           crossFadeState: _isCurrent(index) ? CrossFadeState.showSecond : CrossFadeState.showFirst,
           duration: kThemeAnimationDuration,

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

@@ -402,7 +402,7 @@ class _Tab extends StatelessWidget {
 
     Container centeredLabel = new Container(
       child: new Center(child: labelContent, widthFactor: 1.0, heightFactor: 1.0),
-      constraints: new BoxConstraints(minWidth: _kMinTabWidth),
+      constraints: const BoxConstraints(minWidth: _kMinTabWidth),
       padding: _kTabLabelPadding
     );
 
@@ -512,7 +512,7 @@ class TabBarSelection<T> extends StatefulWidget {
   /// TabBarSelectionState<Foo> tabState = TabBarSelection.of/*<Foo>*/(context);
   /// ```
   static TabBarSelectionState<dynamic/*=T*/> of/*<T>*/(BuildContext context) {
-    return context.ancestorStateOfType(new TypeMatcher<TabBarSelectionState<dynamic/*=T*/>>());
+    return context.ancestorStateOfType(const TypeMatcher<TabBarSelectionState<dynamic/*=T*/>>());
   }
 
   @override
@@ -1302,7 +1302,7 @@ class TabPageSelector<T> extends StatelessWidget {
     return new Container(
       width: 12.0,
       height: 12.0,
-      margin: new EdgeInsets.all(4.0),
+      margin: const EdgeInsets.all(4.0),
       decoration: new BoxDecoration(
         backgroundColor: background,
         border: new Border.all(color: selectedColor.end),

packages/flutter/lib/src/painting/flutter_logo.dart

@@ -258,7 +258,7 @@ class _FlutterLogoPainter extends BoxPainter {
       )
     );
     _textPainter.layout();
-    final ui.TextBox textSize = _textPainter.getBoxesForSelection(new TextSelection(baseOffset: 0, extentOffset: kLabel.length)).single;
+    final ui.TextBox textSize = _textPainter.getBoxesForSelection(const TextSelection(baseOffset: 0, extentOffset: kLabel.length)).single;
     _textBoundingRect = new Rect.fromLTRB(textSize.left, textSize.top, textSize.right, textSize.bottom);
   }
 

packages/flutter/lib/src/rendering/stack.dart

@@ -52,7 +52,7 @@ class RelativeRect {
   }
 
   /// A rect that covers the entire container.
-  static final RelativeRect fill = new RelativeRect.fromLTRB(0.0, 0.0, 0.0, 0.0);
+  static final RelativeRect fill = const RelativeRect.fromLTRB(0.0, 0.0, 0.0, 0.0);
 
   /// Distance from the left side of the container to the left side of this rectangle.
   final double left;

packages/flutter/lib/src/widgets/placeholder.dart

@@ -35,6 +35,6 @@ class PlaceholderState extends State<Placeholder> {
   Widget build(BuildContext context) {
     if (_child != null)
       return child;
-    return new SizedBox(width: 0.0, height: 0.0);
+    return const SizedBox(width: 0.0, height: 0.0);
   }
 }