Fix some minor warnings from the analyzer in the framework.

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

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 import 'dart:math' as math;
 import 'dart:sky' as sky;
 import 'dart:typed_data';
 import 'object.dart';
 import 'package:vector_math/vector_math.dart';
 import 'package:sky/framework/net/image_cache.dart' as image_cache;
@@ skipping 18 matching lines @@
   final double right;
   final double bottom;
   final double left;
 
   operator ==(EdgeDims other) => (top == other.top) ||
                                  (right == other.right) ||
                                  (bottom == other.bottom) ||
                                  (left == other.left);
 
   int get hashCode {
-    value = 373;
+    int value = 373;
     value = 37 * value + top.hashCode;
     value = 37 * value + left.hashCode;
     value = 37 * value + bottom.hashCode;
     value = 37 * value + right.hashCode;
     return value;
   }
   String toString() => "EdgeDims($top, $right, $bottom, $left)";
 }
 
 class BoxConstraints {
@@ skipping 40 matching lines @@
     return clamp(min: minHeight, max: maxHeight, value: height);
   }
 
   sky.Size constrain(sky.Size size) {
     return new sky.Size(constrainWidth(size.width), constrainHeight(size.height));
   }
 
   bool get isInfinite => maxWidth >= double.INFINITY || maxHeight >= double.INFINITY;
 
   int get hashCode {
-    value = 373;
+    int value = 373;
     value = 37 * value + minWidth.hashCode;
     value = 37 * value + maxWidth.hashCode;
     value = 37 * value + minHeight.hashCode;
     value = 37 * value + maxHeight.hashCode;
     return value;
   }
   String toString() => "BoxConstraints($minWidth<=w<$maxWidth, $minHeight<=h<$maxHeight)";
 }
 
 class BoxParentData extends ParentData {
@@ skipping 214 matching lines @@
       double height = requestedSize.height == null ? 0.0 : requestedSize.height;
       size = constraints.constrain(new sky.Size(width, height));
       return;
     }
 
     // If neither height nor width are specified, use inherent image dimensions
     // If only one dimension is specified, adjust the other dimension to
     // maintain the aspect ratio
     if (requestedSize.width == null) {
       if (requestedSize.height == null) {
-        size = constraints.constrain(new sky.Size(_image.width, _image.height));
+        size = constraints.constrain(new sky.Size(_image.width.toDouble(), _image.height.toDouble()));
       } else {
         double width = requestedSize.height * _image.width / _image.height;
         size = constraints.constrain(new sky.Size(width, requestedSize.height));
       }
     } else if (requestedSize.height == null) {
       double height = requestedSize.width * _image.height / _image.width;
       size = constraints.constrain(new sky.Size(requestedSize.width, height));
     } else {
       size = constraints.constrain(requestedSize);
     }
@@ skipping 337 matching lines @@
 
   void defaultPaint(RenderObjectDisplayList canvas) {
     RenderBox child = firstChild;
     while (child != null) {
       assert(child.parentData is ParentDataType);
       canvas.paintChild(child, child.parentData.position);
       child = child.parentData.nextSibling;
     }
   }
 }