Make Text size to its content instead of always 100% width

sky/sdk/lib/framework/rendering/paragraph.dart

Index: sky/sdk/lib/framework/rendering/paragraph.dart
diff --git a/sky/sdk/lib/framework/rendering/paragraph.dart b/sky/sdk/lib/framework/rendering/paragraph.dart
index 7f0ba175a66552c505916097b5622051850bced4..f266c337b01261d0f9871bd385dae1481d6c8d0a 100644
--- a/sky/sdk/lib/framework/rendering/paragraph.dart
+++ b/sky/sdk/lib/framework/rendering/paragraph.dart
@@ -52,7 +52,9 @@ class RenderParagraph extends RenderBox {
     _layoutRoot.minHeight = constraints.minHeight;
     _layoutRoot.maxHeight = constraints.maxHeight;
     _layoutRoot.layout();
-    size = constraints.constrain(new Size(_layoutRoot.rootElement.width, _layoutRoot.rootElement.height));
+    // rootElement.width always expands to fill, use maxContentWidth instead.
+    var root = _layoutRoot.rootElement;
+    size = constraints.constrain(new Size(root.maxContentWidth, root.height));
   }
 
   void paint(RenderObjectDisplayList canvas) {