Add unitAboutToCompile() into DartCompilerListener

editor/tools/plugins/com.google.dart.tools.core/src/com/google/dart/tools/core/internal/compiler/SilentDartCompilerListener.java

Index: editor/tools/plugins/com.google.dart.tools.core/src/com/google/dart/tools/core/internal/compiler/SilentDartCompilerListener.java
diff --git a/editor/tools/plugins/com.google.dart.tools.core/src/com/google/dart/tools/core/internal/compiler/SilentDartCompilerListener.java b/editor/tools/plugins/com.google.dart.tools.core/src/com/google/dart/tools/core/internal/compiler/SilentDartCompilerListener.java
deleted file mode 100644
index 0f7a84651ef04e5994d4b48982c6f91a98038eff..0000000000000000000000000000000000000000
--- a/editor/tools/plugins/com.google.dart.tools.core/src/com/google/dart/tools/core/internal/compiler/SilentDartCompilerListener.java
+++ /dev/null
@@ -1,37 +0,0 @@
-/*
- * Copyright (c) 2011, the Dart project authors.
- * 
- * Licensed under the Eclipse Public License v1.0 (the "License"); you may not use this file except
- * in compliance with the License. You may obtain a copy of the License at
- * 
- * http://www.eclipse.org/legal/epl-v10.html
- * 
- * Unless required by applicable law or agreed to in writing, software distributed under the License
- * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
- * or implied. See the License for the specific language governing permissions and limitations under
- * the License.
- */
-package com.google.dart.tools.core.internal.compiler;
-
-import com.google.dart.compiler.DartCompilationError;
-import com.google.dart.compiler.DartCompilerListener;
-import com.google.dart.compiler.ast.DartUnit;
-
-/**
- * Instances of the class <code>SilentDartCompilerListener</code> implement a compiler listener that
- * ignores errors and warnings.
- */
-public class SilentDartCompilerListener extends DartCompilerListener {
-  /**
-   * A compiler listener that can be shared.
-   */
-  public static final SilentDartCompilerListener INSTANCE = new SilentDartCompilerListener();
-
-  @Override
-  public void onError(DartCompilationError event) {
-  }
-
-  @Override
-  public void unitCompiled(DartUnit unit) {
-  }
-}