Move Dart versions of math.min() and math.max() into VM patch file.

runtime/lib/math_patch.dart

 // Copyright (c) 2012, 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.
 
 import "dart:typed_data";
 
 // A VM patch of the dart:math library.
 
+@patch
+T min<T extends num>(T a, T b) {
+  // These partially redundant type checks improve code quality for dart2js.
+  // Most of the improvement is at call sites from the inferred non-null num
+  // return type.

[sra1, 2017/05/05 07:08:23]

Fix this comment to say the VM version is this way for *compatibility with*
dart2js.

+  if (a is! num) throw new ArgumentError(a);
+  if (b is! num) throw new ArgumentError(b);
+
+  if (a > b) return b;
+  if (a < b) return a;
+  if (b is double) {
+    // Special case for NaN and -0.0. If one argument is NaN return NaN.
+    // [min] must also distinguish between -0.0 and 0.0.
+    if (a is double) {
+      if (a == 0.0) {
+        // a is either 0.0 or -0.0. b is either 0.0, -0.0 or NaN.
+        // The following returns -0.0 if either a or b is -0.0, and it
+        // returns NaN if b is NaN.
+        return (a + b) * a * b;
+      }
+    }
+    // Check for NaN and b == -0.0.
+    if (a == 0 && b.isNegative || b.isNaN) return b;
+    return a;
+  }
+  return a;
+}
+
+@patch
+T max<T extends num>(T a, T b) {
+  // These partially redundant type checks improve code quality for dart2js.
+  // Most of the improvement is at call sites from the inferred non-null num
+  // return type.
+  if (a is! num) throw new ArgumentError(a);
+  if (b is! num) throw new ArgumentError(b);
+
+  if (a > b) return a;
+  if (a < b) return b;
+  if (b is double) {
+    // Special case for NaN and -0.0. If one argument is NaN return NaN.
+    // [max] must also distinguish between -0.0 and 0.0.
+    if (a is double) {
+      if (a == 0.0) {
+        // a is either 0.0 or -0.0. b is either 0.0, -0.0, or NaN.
+        // The following returns 0.0 if either a or b is 0.0, and it
+        // returns NaN if b is NaN.
+        return a + b;
+      }
+    }
+    // Check for NaN.
+    if (b.isNaN) return b;
+    return a;
+  }
+  // max(-0.0, 0) must return 0.
+  if (b == 0 && a.isNegative) return b;
+  return a;
+}
+
 // If [x] is an [int] and [exponent] is a non-negative [int], the result is
 // an [int], otherwise the result is a [double].
 @patch
 num pow(num x, num exponent) {
   if ((x is int) && (exponent is int) && (exponent >= 0)) {
     return _intPow(x, exponent);
   }
   return _doublePow(x.toDouble(), exponent.toDouble());
 }
 
@@ skipping 196 matching lines @@
   }
 
   bool nextBool() {
     return _getBytes(1).isEven;
   }
 
   // Constants used by the algorithm.
   static const _POW2_32 = 1 << 32;
   static const _POW2_53_D = 1.0 * (1 << 53);
 }