Add constructors to signatures

lib/runtime/dart_runtime.js

Index: lib/runtime/dart_runtime.js
diff --git a/lib/runtime/dart_runtime.js b/lib/runtime/dart_runtime.js
index 255d61964ea7f6c2923ccc2f359d1333c4eb336e..4d0aa208d41ca4f43b0e48acd2b7837d88f2b6f6 100644
--- a/lib/runtime/dart_runtime.js
+++ b/lib/runtime/dart_runtime.js
@@ -997,6 +997,7 @@ var dart, _js_helper, _js_primitives;
   }
   dart.generic = generic;
 
+  let _constructorSig = Symbol('sigCtor');
   let _methodSig = Symbol("sig");
   let _staticSig = Symbol("sigStatic");
 
@@ -1017,6 +1018,22 @@ var dart, _js_helper, _js_primitives;
     return sig;
   }
 
+  /// Get the type of a constructor from a class using the stored signature
+  /// If name is undefined, returns the type of the default constructor
+  /// Returns undefined if the constructor is not found.
+  function _getConstructorType(cls, name) {
+    if(!name) name = cls.name;
+    if (cls === void 0) return void 0;
+    if (cls == null) return void 0;
+    let sigCtor = cls[_constructorSig];
+    if (sigCtor === void 0) return void 0;
+    let parts = sigCtor[name];
+    if (parts === void 0) return void 0;
+    let sig = functionType.apply(null, parts);
+    return sig;
+  }
+  dart.classGetConstructorType = _getConstructorType;
+
   /// Given an object and a method name, tear off the method.
   /// Sets the runtime type of the torn off method appropriately,
   /// and also binds the object.
@@ -1039,6 +1056,11 @@ var dart, _js_helper, _js_primitives;
     });
   }
 
+  // Set up the constructor signature field on the constructor
+  function _setConstructorSignature(f, sigF) {
+    defineMemoizedGetter(f, _constructorSig, sigF);
+  }
+
   // Set up the static signature field on the constructor
   function _setStaticSignature(f, sigF) {
     defineMemoizedGetter(f, _staticSig, sigF);
@@ -1066,12 +1088,15 @@ var dart, _js_helper, _js_primitives;
   ///   permit eagerly setting the runtimeType field on the methods
   ///   while still lazily computing the type descriptor object.
   function setSignature(f, signature) {
+    let constructors =
+      ('constructors' in signature) ? signature.constructors : () => ({});
     let methods =
       ('methods' in signature) ? signature.methods : () => ({});
     let statics =
       ('statics' in signature) ? signature.statics : () => ({});
     let names =
       ('names' in signature) ? signature.names : [];
+    _setConstructorSignature(f, constructors);
     _setMethodSignature(f, methods);
     _setStaticSignature(f, statics);
     _setStaticTypes(f, names);