Remove backends.

compiler/java/com/google/dart/compiler/backend/js/ast/JsNullLiteral.java

Index: compiler/java/com/google/dart/compiler/backend/js/ast/JsNullLiteral.java
diff --git a/compiler/java/com/google/dart/compiler/backend/js/ast/JsNullLiteral.java b/compiler/java/com/google/dart/compiler/backend/js/ast/JsNullLiteral.java
deleted file mode 100644
index 506b2e3f330f6dcf6469be42bf5ec775c5af680d..0000000000000000000000000000000000000000
--- a/compiler/java/com/google/dart/compiler/backend/js/ast/JsNullLiteral.java
+++ /dev/null
@@ -1,46 +0,0 @@
-// Copyright (c) 2011, 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.
-
-package com.google.dart.compiler.backend.js.ast;
-
-/**
- * A JavaScript null literal.
- */
-public final class JsNullLiteral extends JsValueLiteral {
-
-  // Should only be instantiated in JsProgram
-  JsNullLiteral() {
-  }
-
-  @Override
-  public boolean isBooleanFalse() {
-    return true;
-  }
-
-  @Override
-  public boolean isBooleanTrue() {
-    return false;
-  }
-
-  @Override
-  public boolean isDefinitelyNotNull() {
-    return false;
-  }
-
-  @Override
-  public boolean isDefinitelyNull() {
-    return true;
-  }
-
-  @Override
-  public void traverse(JsVisitor v, JsContext ctx) {
-    v.visit(this, ctx);
-    v.endVisit(this, ctx);
-  }
-
-  @Override
-  public NodeKind getKind() {
-    return NodeKind.NULL;
-  }
-}