Add fromIterable(s) constructors in SplayTreeMap and LinkedHashMap.

sdk/lib/collection/linked_hash_map.dart

Index: sdk/lib/collection/linked_hash_map.dart
diff --git a/sdk/lib/collection/linked_hash_map.dart b/sdk/lib/collection/linked_hash_map.dart
index 3082ce0881a8b99736968e9a37839bb375c80bbb..7425c18c917c912e26ec4c5c7b3c6ad9376c347a 100644
--- a/sdk/lib/collection/linked_hash_map.dart
+++ b/sdk/lib/collection/linked_hash_map.dart
@@ -25,6 +25,19 @@ class LinkedHashMap<K, V> implements Map<K, V> {
     return new LinkedHashMap<K, V>()..addAll(other);
   }
 
+  factory LinkedHashMap.fromIterable(Iterable iterable,
+      {K key(element), V value(element)}) {
+    LinkedHashMap<K, V> map = new LinkedHashMap<K, V>();
+    Maps._fillMapWithMappedIterable(map, iterable, key: key, value: value);
+    return map;
+  }
+
+  factory LinkedHashMap.fromIterables(Iterable<K> keys, Iterable<V> values) {
+    LinkedHashMap<K, V> map = new LinkedHashMap<K, V>();
+    Maps._fillMapWithIterables(map, keys, values);
+    return map;
+  }
+
   external bool containsKey(Object key);
 
   external bool containsValue(Object value);