Roll engine to f7685ddf16ccf9e5f6c4386c23061b02ed0e37d4.

bin/internal/engine.version

-6388e928801dece14033b9ca99421f473e1d2fd0
+f7685ddf16ccf9e5f6c4386c23061b02ed0e37d4

dev/bots/docs.sh

@@ -10,7 +10,7 @@ set -e
 bin/flutter --version
 
 # Install dartdoc.
-bin/cache/dart-sdk/bin/pub global activate dartdoc 0.13.0+1
+bin/cache/dart-sdk/bin/pub global activate dartdoc 0.13.0+3
 
 # This script generates a unified doc set, and creates
 # a custom index.html, placing everything into dev/docs/doc.

packages/flutter/test/rendering/recording_canvas.dart

@@ -132,6 +132,8 @@ class _MethodCall implements Invocation {
   Map<Symbol, dynamic> get namedArguments => <Symbol, dynamic>{};
   @override
   List<dynamic> get positionalArguments => _arguments;
+  @override
+  List<Type> get typeArguments => throw new UnimplementedError();
 }
 
 String _valueName(Object value) {