Revert type hierarchy changes

sdk/lib/typed_data/dart2js/typed_data_dart2js.dart

Index: sdk/lib/typed_data/dart2js/typed_data_dart2js.dart
diff --git a/sdk/lib/typed_data/dart2js/typed_data_dart2js.dart b/sdk/lib/typed_data/dart2js/typed_data_dart2js.dart
index 022231141a4c95fc88d76deaa343051a93e6c556..5933b2ef060271e2e97a6d159e660d7c946ee95a 100644
--- a/sdk/lib/typed_data/dart2js/typed_data_dart2js.dart
+++ b/sdk/lib/typed_data/dart2js/typed_data_dart2js.dart
@@ -563,8 +563,7 @@ class Uint32List
 }
 
 
-class Uint8ClampedList extends TypedData with ListMixin<int>,
-    FixedLengthListMixin<int> implements JavaScriptIndexingBehavior, List<int>
+class Uint8ClampedList extends Uint8List
     native "Uint8ClampedArray,CanvasPixelArray" {
   factory Uint8ClampedList(int length) => _create1(length);
 
@@ -579,7 +578,8 @@ class Uint8ClampedList extends TypedData with ListMixin<int>,
 
   static const int BYTES_PER_ELEMENT = 1;
 
-  int get length => JS("int", '#(#)', fetchLength, this);
+  // Use implementation from Uint8List
+  // final int length;
 
   int operator[](int index) {
     _checkIndex(index, length);
@@ -660,21 +660,6 @@ class Uint8List
 }
 
 
-class _Uint8ListSubclass extends Uint8List native "Uint8Array_bogus_subclass" {
-  // The Typed Array specification states that Uint8ClampedArray is _not_
-  // a subclass of Uint8Array and is a subclass of ArrayBufferView.
-  // However, some browsers have implemented Uint8ClampedArray as a subclass of
-  // Uint8Array. Dart follows the specification but in order for dart2js to
-  // generate correct code it needs to know that there might be a subclass of
-  // Uint8Array. See: https://codereview.chromium.org/23093027/
-
-  // Factory constructor is unused but needed since a default
-  // (generative) constructor can't be generated for a class
-  // extending a class with no generative constructor.
-  factory _Uint8ListSubclass() => null;
-}
-
-
 class Int64List extends TypedData implements JavaScriptIndexingBehavior, List<int> {
   factory Int64List(int length) {
     throw new UnsupportedError("Int64List not supported by dart2js.");