Sped up hashCode by removing megamorphic call to _identityHashCode.

runtime/lib/double.dart

Index: runtime/lib/double.dart
diff --git a/runtime/lib/double.dart b/runtime/lib/double.dart
index cbf955dc81a4d791d6cfd36ea6e780aefc2236a7..71fddca77c0c44e14ac7f5da7a434f27d0be24d5 100644
--- a/runtime/lib/double.dart
+++ b/runtime/lib/double.dart
@@ -8,10 +8,10 @@ class _Double implements double {
 
   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());
   }