Make Iterable.toList more efficient if the length is known.

runtime/lib/typed_data.dart

Index: runtime/lib/typed_data.dart
diff --git a/runtime/lib/typed_data.dart b/runtime/lib/typed_data.dart
index c4b532f289ee2a0ba144bbf43124be243fac2baf..ad0d89aa2776fa4b18b413640bc9b2aea84f6370 100644
--- a/runtime/lib/typed_data.dart
+++ b/runtime/lib/typed_data.dart
@@ -735,6 +735,14 @@ class _IntListMixin {
   }
 
   Iterator<int> get iterator => new _TypedListIterator<int>(this);
+
+  List<int> toList({bool growable: true}) {
+    return new List<int>.from(this, growable: growable);
+  }
+
+  Set<int> toSet() {
+    return new Set<int>.from(this);
+  }
 }
 
 
@@ -762,6 +770,14 @@ class _DoubleListMixin {
   }
 
   Iterator<double> get iterator => new _TypedListIterator<double>(this);
+
+  List<double> toList({bool growable: true}) {
+    return new List<double>.from(this, growable: growable);
+  }
+
+  Set<double> toSet() {
+    return new Set<double>.from(this);
+  }
 }
 
 
@@ -790,6 +806,14 @@ class _Float32x4ListMixin {
   }
 
   Iterator<Float32x4> get iterator => new _TypedListIterator<Float32x4>(this);
+
+  List<Float32x4> toList({bool growable: true}) {
+    return new List<Float32x4>.from(this, growable: growable);
+  }
+
+  Set<Float32x4> toSet() {
+    return new Set<Float32x4>.from(this);
+  }
 }
 
 
@@ -817,6 +841,14 @@ class _Int32x4ListMixin {
   }
 
   Iterator<Int32x4> get iterator => new _TypedListIterator<Int32x4>(this);
+
+  List<Int32x4> toList({bool growable: true}) {
+    return new List<Int32x4>.from(this, growable: growable);
+  }
+
+  Set<Int32x4> toSet() {
+    return new Set<Int32x4>.from(this);
+  }
 }
 
 
@@ -845,6 +877,14 @@ class _Float64x2ListMixin {
   }
 
   Iterator<Float64x2> get iterator => new _TypedListIterator<Float64x2>(this);
+
+  List<Float64x2> toList({bool growable: true}) {
+    return new List<Float64x2>.from(this, growable: growable);
+  }
+
+  Set<Float64x2> toSet() {
+    return new Set<Float64x2>.from(this);
+  }
 }
 
 
@@ -1146,7 +1186,6 @@ class Uint8List extends _TypedList with _IntListMixin implements List<int>, Type
     return Uint8List.BYTES_PER_ELEMENT;
   }
 
-
   // Internal utility methods.
 
   Uint8List _createList(int length) {