Move hashCode and runtimeType into new interceptors scheme.

sdk/lib/_internal/compiler/implementation/lib/js_number.dart

Index: sdk/lib/_internal/compiler/implementation/lib/js_number.dart
===================================================================
--- sdk/lib/_internal/compiler/implementation/lib/js_number.dart	(revision 15142)
+++ sdk/lib/_internal/compiler/implementation/lib/js_number.dart	(working copy)
@@ -117,6 +117,8 @@
       return JS('String', r'String(#)', this);
     }
   }
+
+  int get hashCode => this & 0x1FFFFFFF;
 }
 
 class JSInt extends JSNumber {
@@ -125,8 +127,11 @@
   bool get isEven => (this & 1) == 0;
 
   bool get isOdd => (this & 1) == 1;
+
+  Type get runtimeType => createRuntimeType('int');
 }
 
 class JSDouble extends JSNumber {
   const JSDouble();
+  Type get runtimeType => createRuntimeType('double');
 }