Use relative URIs for core library part-of statements.

sdk/lib/math/rectangle.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
-part of dart.math;
+
+part of "math.dart";
 
 /**
  * A base class for representing two-dimensional axis-aligned rectangles.
  *
  * This rectangle uses a left-handed Cartesian coordinate system, with x
  * directed to the right and y directed down, as per the convention in 2D
  * computer graphics.
  *
  * See also:
  *    [W3C Coordinate Systems Specification](http://www.w3.org/TR/SVG/coords.html#InitialCoordinateSystem).
@@ skipping 250 matching lines @@
 
 /**
  * Converts a negative [int] or [double] to a zero-value of the same type.
  *
  * Returns `0` if value is int, `0.0` if value is double.
  */
 T _clampToZero<T extends num>(T value) {
   assert(value < 0);
   return -value * 0;
 }