Sped up hashCode by removing megamorphic call to _identityHashCode.

runtime/lib/double.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.
 
 class _Double implements double {
   factory _Double.fromInteger(int value)
       native "Double_doubleFromInteger";
 
   Type get runtimeType => double;
 
-  int get _identityHashCode {
-    if (isNaN || isInfinite) return 0;
-    return toInt();
-  }
+  // Code is replicated to avoid unnecessary dispath overhead.

[sra1, 2016/07/08 21:35:59]

They could both call a common static method.
Since there is an open bug on the simplistic implementation
(https://github.com/dart-lang/sdk/issues/2884) the implementation is likely to
become more complicated for non-integral values.

[bakster, 2016/07/08 22:04:22]

I'll add a todo in the code for now. A static only makes sense when the code
gets more complicated.

+  int get hashCode => (isNaN || isInfinite) ?  0 : toInt();
+  int get _identityHashCode => (isNaN || isInfinite) ?  0 : toInt();
+
   double operator +(num other) {
     return _add(other.toDouble());
   }
   double _add(double other) native "Double_add";
 
   double operator -(num other) {
     return _sub(other.toDouble());
   }
   double _sub(double other) native "Double_sub";
 
@@ skipping 244 matching lines @@
         return EQUAL;
       }
     } else if (isNaN) {
       return other.isNaN ? EQUAL : GREATER;
     } else {
       // Other is NaN.
       return LESS;
     }
   }
 }