Remove code supporting incremental compilation in dart2js

pkg/compiler/lib/src/closure.dart

Index: pkg/compiler/lib/src/closure.dart
diff --git a/pkg/compiler/lib/src/closure.dart b/pkg/compiler/lib/src/closure.dart
index 8cec93b45be82e87191ce1e125f2e1bdbb996224..566a754d96a2cc43f2541533cc813ac659f0cf4c 100644
--- a/pkg/compiler/lib/src/closure.dart
+++ b/pkg/compiler/lib/src/closure.dart
@@ -115,19 +115,6 @@ class ClosureTask extends CompilerTask {
       });
     });
   }
-
-  void forgetElement(var closure) {
-    ClosureClassElement cls;
-    if (closure is ClosureFieldElement) {
-      cls = closure.closureClass;
-    } else if (closure is SynthesizedCallMethodElementX) {
-      cls = closure.closureClass;
-    } else {
-      throw new SpannableAssertionFailure(
-          closure, 'Not a closure: $closure (${closure.runtimeType}).');
-    }
-    compiler.enqueuer.codegen.forgetEntity(cls, compiler);
-  }
 }
 
 /// Common interface for [BoxFieldElement] and [ClosureFieldElement] as