Split getIntrinsicDimensions into four pieces

This CL splits getIntrinsicDimensions into getMinIntrinsicWidth,
getMaxIntrinsicWidth, getMinIntrinsicHeight, and getMaxIntrinsicHeight so that
we can properly shrink-wrap the stocks app menu. This CL just contains the
refactoring. The use in stocks app will come in a later CL.

R=ianh@google.com

Review URL: https://codereview.chromium.org/1167293003

examples/lib/solid_color_box.dart

@@ -13,8 +13,20 @@ class RenderSolidColorBox extends RenderDecoratedBox {
       : backgroundColor = backgroundColor,
         super(decoration: new BoxDecoration(backgroundColor: backgroundColor));
 
-  Size getIntrinsicDimensions(BoxConstraints constraints) {
-    return constraints.constrain(desiredSize);
+  double getMinIntrinsicWidth(BoxConstraints constraints) {
+    return constraints.constrainWidth(desiredSize.width);
+  }
+
+  double getMaxIntrinsicWidth(BoxConstraints constraints) {
+    return constraints.constrainWidth(desiredSize.width);
+  }
+
+  double getMinIntrinsicHeight(BoxConstraints constraints) {
+    return constraints.constrainHeight(desiredSize.height);
+  }
+
+  double getMaxIntrinsicHeight(BoxConstraints constraints) {
+    return constraints.constrainHeight(desiredSize.height);
   }
 
   void performLayout() {