Cleaned up a few analyzer warnings

sky/sdk/lib/rendering/paragraph.dart

Index: sky/sdk/lib/rendering/paragraph.dart
diff --git a/sky/sdk/lib/rendering/paragraph.dart b/sky/sdk/lib/rendering/paragraph.dart
index 22bd617f69c54783d62f7df80f191b18f766c274..f7abf7dd40247953a447eb58dc42797ef20ff218 100644
--- a/sky/sdk/lib/rendering/paragraph.dart
+++ b/sky/sdk/lib/rendering/paragraph.dart
@@ -103,7 +103,7 @@ class TextStyle {
   }
 }
 
-class InlineBase {
+abstract class InlineBase {
   sky.Node _toDOM(sky.Document owner);
   String toString([String prefix = '']);
 }
@@ -182,7 +182,7 @@ class RenderParagraph extends RenderBox {
     markNeedsLayout();
   }
 
-  sky.Element _layout(BoxConstraints constraints) {
+  void _layout(BoxConstraints constraints) {
     _layoutRoot.maxWidth = constraints.maxWidth;
     _layoutRoot.minWidth = constraints.minWidth;
     _layoutRoot.minHeight = constraints.minHeight;