Use a JS dictionary to initialize a the fields in a Mojo struct

mojo/public/js/bindings/struct_unittests.js

+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+define([
+    "gin/test/expect",
+    "mojo/public/interfaces/bindings/tests/rect.mojom",
+    "mojo/public/interfaces/bindings/tests/test_structs.mojom"
+], function(expect,
+            rect,
+            testStructs) {
+
+  function testConstructors() {
+    var r = new rect.Rect();
+    expect(r).toEqual(new rect.Rect({x:0, y:0, width:0, height:0}));
+    expect(r).toEqual(new rect.Rect({foo:100, bar:200}));
+
+    r.x = 10;
+    r.y = 20;
+    r.width = 30;
+    r.height = 40;
+    var rp = new testStructs.RectPair({first: r, second: r});
+    expect(rp.first).toEqual(r);
+    expect(rp.second).toEqual(r);
+
+    expect(new testStructs.RectPair({second: r}).first).toBeNull();
+
+    var nr = new testStructs.NamedRegion();
+    // TODO(hansmuller): nr.name should be null, see crbug.com/417039.
+    expect(nr.name).toBe("");
+    expect(nr.rects).toBeNull();
+    expect(nr).toEqual(new testStructs.NamedRegion({}));
+
+    nr.name = "foo";
+    nr.rects = [r, r, r];
+    expect(nr).toEqual(new testStructs.NamedRegion({
+      name: "foo",
+      rects: [r, r, r],
+    }));
+
+    var e = new testStructs.EmptyStruct();
+    expect(e).toEqual(new testStructs.EmptyStruct({foo:123}));
+  }
+
+  testConstructors();
+  this.result = "PASS";
+});