Always use / with URI

compiler/java/com/google/dart/compiler/UrlDartSource.java

Index: compiler/java/com/google/dart/compiler/UrlDartSource.java
diff --git a/compiler/java/com/google/dart/compiler/UrlDartSource.java b/compiler/java/com/google/dart/compiler/UrlDartSource.java
index 8d0913b22b91180e4ae3dde0bff5a3ffcca85083..80e3e8374a954b0b2d80b6647b74a621e5e8cef4 100644
--- a/compiler/java/com/google/dart/compiler/UrlDartSource.java
+++ b/compiler/java/com/google/dart/compiler/UrlDartSource.java
@@ -41,7 +41,7 @@ public class UrlDartSource extends UrlSource implements DartSource {
   public String getName() {
     try {
       String uriSafeName = new URI(null, null, relPath, null).toString();
-      return lib.getName() + File.separatorChar + uriSafeName;
+      return lib.getName() + "/" + uriSafeName;
     } catch (URISyntaxException e) {
       throw new AssertionError(e);
     }