Add a command-line option for generating source maps.

compiler/javatests/com/google/dart/compiler/common/GenerateSourceMapTest.java

Index: compiler/javatests/com/google/dart/compiler/common/GenerateSourceMapTest.java
===================================================================
--- compiler/javatests/com/google/dart/compiler/common/GenerateSourceMapTest.java	(revision 471)
+++ compiler/javatests/com/google/dart/compiler/common/GenerateSourceMapTest.java	(working copy)
@@ -8,9 +8,11 @@
 import com.google.common.collect.Maps;
 import com.google.common.io.CharStreams;
 import com.google.dart.compiler.Backend;
+import com.google.dart.compiler.CompilerConfiguration;
 import com.google.dart.compiler.CompilerTestCase;
 import com.google.dart.compiler.DartArtifactProvider;
 import com.google.dart.compiler.DartSource;
+import com.google.dart.compiler.DefaultCompilerConfiguration;
 import com.google.dart.compiler.MockArtifactProvider;
 import com.google.dart.compiler.backend.dart.DartBackend;
 import com.google.dart.compiler.backend.js.ClosureJsBackend;
@@ -275,6 +277,15 @@
     }
   }
 
+  @Override
+  protected CompilerConfiguration getCompilerConfiguration(Backend backend) {
+    return new DefaultCompilerConfiguration(
+        backend, new com.google.dart.compiler.CommandLineOptions.CompilerOptions(){
+          @Override
+          public boolean generateSourceMaps() { return true; }
+        });
+  }
+
   protected RunResult getResultForCompile(String fileName, String sourceCode, String part,
       Backend backend, String outExt, String mapExt) throws Exception {
     DartArtifactProvider provider = new MockArtifactProvider();