Make 'where' lazy.

sdk/lib/html/src/_Collections.dart

Index: sdk/lib/html/src/_Collections.dart
diff --git a/sdk/lib/html/src/_Collections.dart b/sdk/lib/html/src/_Collections.dart
index e24029df9743453e2e5239db7e3a2da01aeeec1c..44d5f880669287e69a3c6af59ce7e759a124932a 100644
--- a/sdk/lib/html/src/_Collections.dart
+++ b/sdk/lib/html/src/_Collections.dart
@@ -23,10 +23,6 @@ class _Collections {
     }
   }
 
-  static Iterable mappedBy(Iterable<Object> source, f(o)) {
-    return new MappedIterable(source, f);
-  }
-
   static bool some(Iterable<Object> iterable, bool f(Object o)) {
     for (final e in iterable) {
       if (f(e)) return true;
@@ -41,15 +37,6 @@ class _Collections {
     return true;
   }
 
-  static List where(Iterable<Object> source,
-                     List<Object> destination,
-                     bool f(o)) {
-    for (final e in source) {
-      if (f(e)) destination.add(e);
-    }
-    return destination;
-  }
-
   static bool isEmpty(Iterable<Object> iterable) {
     return !iterable.iterator.moveNext();
   }