Big merge from experimental to bleeding edge.

sdk/lib/core/strings.dart

Index: sdk/lib/core/strings.dart
diff --git a/sdk/lib/core/strings.dart b/sdk/lib/core/strings.dart
index 9d565a1e22a7f0f4cc717456dc2c7127a9768d71..dcdcafc4cfcb08a97a7d777b92b794c122a611ea 100644
--- a/sdk/lib/core/strings.dart
+++ b/sdk/lib/core/strings.dart
@@ -8,10 +8,10 @@ abstract class Strings {
   /**
    * Joins all the given strings to create a new string.
    */
-  external static String join(List<String> strings, String separator);
+  external static String join(Iterable<String> strings, String separator);
 
   /**
    * Concatenates all the given strings to create a new string.
    */
-  external static String concatAll(List<String> strings);
+  external static String concatAll(Iterable<String> strings);
 }