translate uris pointing to non-existing dart libraries

compiler/java/com/google/dart/compiler/SystemLibraryManager.java

Index: compiler/java/com/google/dart/compiler/SystemLibraryManager.java
===================================================================
--- compiler/java/com/google/dart/compiler/SystemLibraryManager.java	(revision 10120)
+++ compiler/java/com/google/dart/compiler/SystemLibraryManager.java	(working copy)
@@ -311,10 +311,13 @@
     if (isDartUri(uri)) {
       String host = uri.getHost();
       SystemLibrary library = hostMap.get(host);
-      if (library == null) {
-        throw new RuntimeException("No system library defined for " + uri);
+      if (library != null) {
+        return library.translateUri(uri);
       }
-      return library.translateUri(uri);
+      if (host != null) {
+        return new File(getSdkLibPath(), host).toURI().resolve("." + uri.getPath());
+      }
+      throw new RuntimeException("No system library defined for " + uri);
     } 
     if (isPackageUri(uri)){   
       URI fileUri;