Remove backends.

compiler/java/com/google/dart/compiler/backend/js/JsNamer.java

-// 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;
-
-import com.google.dart.compiler.backend.js.ast.JsProgram;
-
-/**
- * A namer runs through a program and renames the short names of JsNames.
- * Namers must assign short names that don't clash and that are valid
- * JS-identifiers. Nested JsScopes must not shadow JsNames from outer
- * scopes.
- * If a JsName is marked as non-obfuscatable then it must retain its short
- * name.
- */
-public interface JsNamer {
-  /**
-   * Names the shortNames of all JsNames of the program so that they are valid
-   * JS-identifiers and that there are no clashes and no shadowing.
-   */
-  public void exec(JsProgram program);
-}