Remove backends.

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

Index: compiler/java/com/google/dart/compiler/backend/js/ast/JsThisRef.java
diff --git a/compiler/java/com/google/dart/compiler/backend/js/ast/JsThisRef.java b/compiler/java/com/google/dart/compiler/backend/js/ast/JsThisRef.java
deleted file mode 100644
index 9adb64594884d37c73bc8991f56156739856a001..0000000000000000000000000000000000000000
--- a/compiler/java/com/google/dart/compiler/backend/js/ast/JsThisRef.java
+++ /dev/null
@@ -1,51 +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 <code>this</code> reference.
- */
-public final class JsThisRef extends JsValueLiteral {
-
-  public JsThisRef() {
-    super();
-  }
-
-  @Override
-  public boolean isBooleanFalse() {
-    return false;
-  }
-
-  @Override
-  public boolean isBooleanTrue() {
-    return true;
-  }
-
-  @Override
-  public boolean isDefinitelyNotNull() {
-    /*
-     * You'd think that you could get a null this via function.call/apply, but
-     * in fact you can't: they just make this be the window object instead. So
-     * it really can't ever be null.
-     */
-    return true;
-  }
-
-  @Override
-  public boolean isDefinitelyNull() {
-    return false;
-  }
-
-  @Override
-  public void traverse(JsVisitor v, JsContext ctx) {
-    v.visit(this, ctx);
-    v.endVisit(this, ctx);
-  }
-
-  @Override
-  public NodeKind getKind() {
-    return NodeKind.THIS;
-  }
-}