Remove unneeded types (#949)

web/github_dataviz/lib/catmull.dart

@@ -60,7 +60,7 @@ class CatmullInterpolator implements Interpolator {
   }
 
   static void test() {
-    List<Point2D> controlPoints = <Point2D>[];
+    final controlPoints = <Point2D>[];
     controlPoints.add(Point2D(-1, 1));
     controlPoints.add(Point2D(0, 1));
     controlPoints.add(Point2D(1, -1));

web/github_dataviz/lib/layered_chart.dart

@@ -49,9 +49,9 @@ class LayeredChartState extends State<LayeredChart> {
     graphHeight = MathUtils.clampedMap(screenRatio, 0.5, 2.5, 50, 150);
 
     int m = dataToPlot.length;
-    paths = <Path>[];
-    capPaths = <Path>[];
-    maxValues = <double>[];
+    paths = [];
+    capPaths = [];
+    maxValues = [];
     for (int i = 0; i < m; i++) {
       int n = dataToPlot[i].series.length;
       maxValues.add(0);
@@ -71,11 +71,11 @@ class LayeredChartState extends State<LayeredChart> {
     double xWidth = (endX - startX) / numPoints;
     double capRangeX = capSize * cos(capTheta);
     double tanCapTheta = tan(capTheta);
-    List<double> curvePoints = <double>[];
+    final curvePoints = <double>[];
     for (int i = 0; i < m; i++) {
       List<int> series = dataToPlot[i].series;
       int n = series.length;
-      List<Point2D> controlPoints = <Point2D>[];
+      final controlPoints = <Point2D>[];
       controlPoints.add(Point2D(-1, 0));
       double last = 0;
       for (int j = 0; j < n; j++) {
@@ -135,7 +135,7 @@ class LayeredChartState extends State<LayeredChart> {
       capPaths[i].lineTo(startX, startY + 1);
       capPaths[i].close();
     }
-    labelPainter = <TextPainter>[];
+    labelPainter = [];
     for (int i = 0; i < dataToPlot.length; i++) {
       TextSpan span = TextSpan(
           style: const TextStyle(
@@ -148,7 +148,7 @@ class LayeredChartState extends State<LayeredChart> {
       tp.layout();
       labelPainter.add(tp);
     }
-    milestonePainter = <TextPainter>[];
+    milestonePainter = [];
     for (int i = 0; i < milestones.length; i++) {
       TextSpan span = TextSpan(
           style: const TextStyle(

web/github_dataviz/lib/main.dart

@@ -48,7 +48,7 @@ class _MainLayoutState extends State<MainLayout> with TickerProviderStateMixin {
 
     createAnimation(0);
 
-    weekLabels = <WeekLabel>[];
+    weekLabels = [];
     weekLabels.add(WeekLabel.forDate(DateTime(2019, 2, 26), 'v1.2'));
     weekLabels.add(WeekLabel.forDate(DateTime(2018, 12, 4), 'v1.0'));
 //    weekLabels.add(WeekLabel.forDate(new DateTime(2018, 9, 19), "Preview 2"));
@@ -155,7 +155,7 @@ class _MainLayoutState extends State<MainLayout> with TickerProviderStateMixin {
     Column mainColumn = Column(
       mainAxisAlignment: MainAxisAlignment.center,
       mainAxisSize: MainAxisSize.max,
-      children: <Widget>[
+      children: [
         Expanded(child: layeredChart),
         Padding(
           padding: const EdgeInsets.only(