Declare a return value of `Uint8List` in `BytesBuilder` methods (#58)

Part of the rollout of https://github.com/dart-lang/sdk/issues/36900
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 794f783..5240a85 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,7 @@
+## 1.0.13
+
+* Internal changes for consistency with the Dart SDK.
+
 ## 1.0.12
 
 * Allow `stream_channel` version 2.x
diff --git a/lib/src/copy/bytes_builder.dart b/lib/src/copy/bytes_builder.dart
index fed15ad..f34df48 100644
--- a/lib/src/copy/bytes_builder.dart
+++ b/lib/src/copy/bytes_builder.dart
@@ -47,12 +47,12 @@
   ///
   /// The list returned is a view of the internal buffer, limited to the
   /// [length].
-  List<int> takeBytes();
+  Uint8List takeBytes();
 
   /// Returns a copy of the current contents of the builder.
   ///
   /// Leaves the contents of the builder intact.
-  List<int> toBytes();
+  Uint8List toBytes();
 
   /// The number of bytes in the builder.
   int get length;
@@ -124,14 +124,14 @@
     _buffer = newBuffer;
   }
 
-  List<int> takeBytes() {
+  Uint8List takeBytes() {
     if (_length == 0) return _emptyList;
     var buffer = Uint8List.view(_buffer.buffer, 0, _length);
     clear();
     return buffer;
   }
 
-  List<int> toBytes() {
+  Uint8List toBytes() {
     if (_length == 0) return _emptyList;
     return Uint8List.fromList(Uint8List.view(_buffer.buffer, 0, _length));
   }
@@ -179,7 +179,7 @@
     _length++;
   }
 
-  List<int> takeBytes() {
+  Uint8List takeBytes() {
     if (_length == 0) return _CopyingBytesBuilder._emptyList;
     if (_chunks.length == 1) {
       var buffer = _chunks[0];
@@ -196,7 +196,7 @@
     return buffer;
   }
 
-  List<int> toBytes() {
+  Uint8List toBytes() {
     if (_length == 0) return _CopyingBytesBuilder._emptyList;
     var buffer = Uint8List(_length);
     int offset = 0;
diff --git a/pubspec.yaml b/pubspec.yaml
index f1551c5..b4cdedc 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,5 +1,5 @@
 name: web_socket_channel
-version: 1.0.12
+version: 1.0.13
 
 description: >-
   StreamChannel wrappers for WebSockets. Provides a cross-platform