Remove RenderSizedBox.

Make old users of RenderSizedBox use RenderConstrainedBox.
Change the semantics of BoxDecoration.apply* to actually apply the provided constraints to the current constraints, rather than the previous behaviour of merging them neutrally.

R=abarth@chromium.org

Review URL: https://codereview.chromium.org/1189603003.

examples/rendering/borders.dart

@@ -16,8 +16,8 @@ void main() {
   var root = new RenderBlock(children: [
     new RenderPadding(
       padding: new EdgeDims.all(10.0),
-      child: new RenderSizedBox(
-        desiredSize: new sky.Size.fromHeight(100.0),
+      child: new RenderConstrainedBox(
+        additionalConstraints: new BoxConstraints.tightFor(height: 100.0),
         child: new RenderDecoratedBox(
           decoration: new BoxDecoration(
             backgroundColor: new sky.Color(0xFFFFFF00)
@@ -27,8 +27,8 @@ void main() {
     ),
     new RenderPadding(
       padding: new EdgeDims.all(10.0),
-      child: new RenderSizedBox(
-        desiredSize: new sky.Size.fromHeight(100.0),
+      child: new RenderConstrainedBox(
+        additionalConstraints: new BoxConstraints.tightFor(height: 100.0),
         child: new RenderDecoratedBox(
           decoration: new BoxDecoration(
             border: new Border(
@@ -44,8 +44,8 @@ void main() {
     ),
     new RenderPadding(
       padding: new EdgeDims.all(10.0),
-      child: new RenderSizedBox(
-        desiredSize: new sky.Size.fromHeight(100.0),
+      child: new RenderConstrainedBox(
+        additionalConstraints: new BoxConstraints.tightFor(height: 100.0),
         child: new RenderDecoratedBox(
           decoration: new BoxDecoration(
             backgroundColor: new sky.Color(0xFFFFFF00)
@@ -55,8 +55,8 @@ void main() {
     ),
     new RenderPadding(
       padding: new EdgeDims.all(10.0),
-      child: new RenderSizedBox(
-        desiredSize: new sky.Size.fromHeight(100.0),
+      child: new RenderConstrainedBox(
+        additionalConstraints: new BoxConstraints.tightFor(height: 100.0),
         child: new RenderDecoratedBox(
           decoration: new BoxDecoration(
             backgroundColor: new sky.Color(0xFFFFFF00)
@@ -66,8 +66,8 @@ void main() {
     ),
     new RenderPadding(
       padding: new EdgeDims.all(10.0),
-      child: new RenderSizedBox(
-        desiredSize: new sky.Size.fromHeight(100.0),
+      child: new RenderConstrainedBox(
+        additionalConstraints: new BoxConstraints.tightFor(height: 100.0),
         child: new RenderDecoratedBox(
           decoration: new BoxDecoration(
             backgroundColor: new sky.Color(0xFFFFFF00)

examples/rendering/transform.dart

@@ -12,9 +12,12 @@ AppView app;
 
 void main() {
   RenderDecoratedBox green = new RenderDecoratedBox(
-      decoration: new BoxDecoration(backgroundColor: const sky.Color(0xFF00FF00)));
-  RenderSizedBox box = new RenderSizedBox(
-      desiredSize: new sky.Size(200.0, 200.0), child: green);
+    decoration: new BoxDecoration(backgroundColor: const sky.Color(0xFF00FF00))
+  );
+  RenderConstrainedBox box = new RenderConstrainedBox(
+    additionalConstraints: new BoxConstraints.tight(const Size(200.0, 200.0)),
+    child: green
+  );
 
   Matrix4 transform = new Matrix4.identity();
   RenderTransform spin = new RenderTransform(