Make is checks work on JavaScriptFunction objects.

pkg/compiler/lib/src/js_backend/js_interop_analysis.dart

Index: pkg/compiler/lib/src/js_backend/js_interop_analysis.dart
diff --git a/pkg/compiler/lib/src/js_backend/js_interop_analysis.dart b/pkg/compiler/lib/src/js_backend/js_interop_analysis.dart
index e2ebe39130a3b4ea5222bcd94f3abdba770da85f..585f98f26a52cde3783f95903955c2a8fa25cec4 100644
--- a/pkg/compiler/lib/src/js_backend/js_interop_analysis.dart
+++ b/pkg/compiler/lib/src/js_backend/js_interop_analysis.dart
@@ -8,6 +8,11 @@ library compiler.src.js_backend.js_interop_analysis;
 import '../common.dart';
 import '../constants/values.dart'
     show ConstantValue, ConstructedConstantValue, StringConstantValue;
+import '../dart_types.dart'
+    show
+        DartType,
+        DynamicType,
+        FunctionType;
 import '../diagnostics/messages.dart' show MessageKind;
 import '../elements/elements.dart'
     show
@@ -185,4 +190,14 @@ class JsInteropAnalysis {
     });
     return new jsAst.Block(statements);
   }
+
+  FunctionType buildJsFunctionType() {
+    // TODO(jacobr): consider using codegenWorld.isChecks to determine the
+    // range of positional arguments that need to be supported by JavaScript
+    // function types.
+    return new FunctionType.synthesized(
+      const DynamicType(),
+      [],
+      new List<DartType>.generate(16, (_) => const DynamicType()));

[sra1, 2016/06/30 17:57:13]

This is ok since it is a one-of thing, but consider List.filled.

[Jacob, 2016/07/01 18:27:50]

filled is better. Forgot we had that constructor.

+  }
 }