Optimize List.toList/.sublist and List.from on lists.

sdk/lib/_internal/lib/core_patch.dart

Index: sdk/lib/_internal/lib/core_patch.dart
diff --git a/sdk/lib/_internal/lib/core_patch.dart b/sdk/lib/_internal/lib/core_patch.dart
index 75b339d9d00b9d5c0a8ed0ecacf33048b95601d4..85ab0b9246ffed5c5d9d55d3223eaf31032a5be7 100644
--- a/sdk/lib/_internal/lib/core_patch.dart
+++ b/sdk/lib/_internal/lib/core_patch.dart
@@ -254,6 +254,16 @@ class List<E> {
     }
     return result;
   }
+
+  @patch
+  factory List.from(Iterable other, { bool growable: true }) {
+    List<E> list = new List<E>();
+    for (E e in other) {
+      list.add(e);
+    }
+    if (growable) return list;
+    return makeListFixedLength(list);
+  }
 }