Re-apply "Implement operator== and hashCode for bound closures."

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

Index: sdk/lib/_internal/compiler/implementation/compiler.dart
===================================================================
--- sdk/lib/_internal/compiler/implementation/compiler.dart	(revision 23383)
+++ sdk/lib/_internal/compiler/implementation/compiler.dart	(working copy)
@@ -306,6 +306,7 @@
 
   ClassElement objectClass;
   ClassElement closureClass;
+  ClassElement boundClosureClass;
   ClassElement dynamicClass;
   ClassElement boolClass;
   ClassElement numClass;
@@ -706,6 +707,7 @@
       return result;
     }
     jsInvocationMirrorClass = lookupHelperClass('JSInvocationMirror');
+    boundClosureClass = lookupHelperClass('BoundClosure');
     closureClass = lookupHelperClass('Closure');
     dynamicClass = lookupHelperClass('Dynamic_');
     nullClass = lookupHelperClass('Null');