Tweaks near Material, BoxDecoration, implicit animations.

Some more asserts and toString info.
Reorder some code to group lerp-related functions.

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

@@ -84,6 +84,7 @@ class Material extends StatefulComponent {
     this.color,
     this.textStyle
   }) : super(key: key) {
+    assert(type != null);
     assert(elevation != null);
   }
 
@@ -100,6 +101,14 @@ class Material extends StatefulComponent {
   }
 
   _MaterialState createState() => new _MaterialState();
+
+  void debugFillDescription(List<String> description) {
+    super.debugFillDescription(description);
+    description.add('$type');
+    description.add('elevation: $elevation');
+    if (color != null)
+      description.add('color: $color');
+  }
 }
 
 class _MaterialState extends State<Material> {

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

@@ -726,32 +726,6 @@ class BoxDecoration extends Decoration {
     );
   }
 
-  double getEffectiveBorderRadius(Rect rect) {
-    double shortestSide = rect.shortestSide;
-    // In principle, we should use shortestSide / 2.0, but we don't want to
-    // run into floating point rounding errors. Instead, we just use
-    // shortestSide and let ui.Canvas do any remaining clamping.
-    return borderRadius > shortestSide ? shortestSide : borderRadius;
-  }
-
-  bool hitTest(Size size, Point position) {
-    assert(shape != null);
-    assert((Point.origin & size).contains(position));
-    switch (shape) {
-      case BoxShape.rectangle:
-        if (borderRadius != null) {
-          ui.RRect bounds = new ui.RRect.fromRectXY(Point.origin & size, borderRadius, borderRadius);
-          return bounds.contains(position);
-        }
-        return true;
-      case BoxShape.circle:
-        // Circles are inscribed into our smallest dimension.
-        Point center = size.center(Point.origin);
-        double distance = (position - center).distance;
-        return distance <= math.min(size.width, size.height) / 2.0;
-    }
-  }
-
   /// Linearly interpolate between two box decorations.
   ///
   /// Interpolates each parameter of the box decoration separately.
@@ -843,6 +817,32 @@ class BoxDecoration extends Decoration {
     backgroundImage?._removeChangeListener(listener);
   }
 
+  double getEffectiveBorderRadius(Rect rect) {
+    double shortestSide = rect.shortestSide;
+    // In principle, we should use shortestSide / 2.0, but we don't want to
+    // run into floating point rounding errors. Instead, we just use
+    // shortestSide and let ui.Canvas do any remaining clamping.
+    return borderRadius > shortestSide ? shortestSide : borderRadius;
+  }
+
+  bool hitTest(Size size, Point position) {
+    assert(shape != null);
+    assert((Point.origin & size).contains(position));
+    switch (shape) {
+      case BoxShape.rectangle:
+        if (borderRadius != null) {
+          ui.RRect bounds = new ui.RRect.fromRectXY(Point.origin & size, borderRadius, borderRadius);
+          return bounds.contains(position);
+        }
+        return true;
+      case BoxShape.circle:
+        // Circles are inscribed into our smallest dimension.
+        Point center = size.center(Point.origin);
+        double distance = (position - center).distance;
+        return distance <= math.min(size.width, size.height) / 2.0;
+    }
+  }
+
   _BoxDecorationPainter createBoxPainter() => new _BoxDecorationPainter(this);
 }
 

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

@@ -75,6 +75,11 @@ abstract class AnimatedWidgetBase extends StatefulComponent {
   final Duration duration;
 
   AnimatedWidgetBaseState createState();
+
+  void debugFillDescription(List<String> description) {
+    super.debugFillDescription(description);
+    description.add('duration: ${duration.inMilliseconds}ms');
+  }
 }
 
 typedef AnimatedValue<T> VariableConstructor<T>(T targetValue);
@@ -232,6 +237,26 @@ class AnimatedContainer extends AnimatedWidgetBase {
   final double height;
 
   _AnimatedContainerState createState() => new _AnimatedContainerState();
+
+  void debugFillDescription(List<String> description) {
+    super.debugFillDescription(description);
+    if (constraints != null)
+      description.add('$constraints');
+    if (decoration != null)
+      description.add('has background');
+    if (foregroundDecoration != null)
+      description.add('has foreground');
+    if (margin != null)
+      description.add('margin: $margin');
+    if (padding != null)
+      description.add('padding: $padding');
+    if (transform != null)
+      description.add('has transform');
+    if (width != null)
+      description.add('width: $width');
+    if (height != null)
+      description.add('height: $height');
+  }
 }
 
 class _AnimatedContainerState extends AnimatedWidgetBaseState<AnimatedContainer> {