Add a command-line option for generating source maps.

compiler/javatests/com/google/dart/compiler/CompilerTestCase.java

Index: compiler/javatests/com/google/dart/compiler/CompilerTestCase.java
===================================================================
--- compiler/javatests/com/google/dart/compiler/CompilerTestCase.java	(revision 471)
+++ compiler/javatests/com/google/dart/compiler/CompilerTestCase.java	(working copy)
@@ -187,13 +187,20 @@
      MockLibrarySource lib = new MockLibrarySource();
      DartSourceTest src = new DartSourceTest(name, code, lib);
      lib.addSource(src);
-     CompilerConfiguration config = new DefaultCompilerConfiguration(backend);
+     CompilerConfiguration config = getCompilerConfiguration(backend);
      DartCompilerListener listener = new DartCompilerListenerTest(src.getName());
      DartCompiler.compileLib(lib, config, provider, listener);
      return src;
   }
 
   /**
+   * Allow tests to override the configuration used.
+   */
+  protected CompilerConfiguration getCompilerConfiguration(Backend backend) {
+    return new DefaultCompilerConfiguration(backend);
+  }
+
+  /**
    * Parse a single compilation unit for the given input file.
    */
   protected final DartUnit parseUnit(final String path) {