Mojo JS bindings: introduce concepts that are more similar to C++ bindings:

mojo/public/js/connection.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("mojo/public/js/connection", [
-  "mojo/public/js/bindings",
   "mojo/public/js/connector",
   "mojo/public/js/core",
   "mojo/public/js/router",
-], function(bindings, connector, core, router) {
+], function(connector, core, router) {
 
   var Router = router.Router;
-  var EmptyProxy = bindings.EmptyProxy;
-  var EmptyStub = bindings.EmptyStub;
-  var ProxyBindings = bindings.ProxyBindings;
-  var StubBindings = bindings.StubBindings;
   var TestConnector = connector.TestConnector;
   var TestRouter = router.TestRouter;
 
+  var kProxyProperties = Symbol("proxyProperties");

[yzshen1, 2016/12/02 00:22:59]

I moved the original contents in bindings.js to this file.
So there is no need to review this one carefully.

Eventually I will remove this entire file. The code is so confusing!!

+  var kStubProperties = Symbol("stubProperties");
+
+  // Public proxy class properties that are managed at runtime by the JS
+  // bindings. See ProxyBindings below.
+  function ProxyProperties(receiver) {
+    this.receiver = receiver;
+  }
+
+  // TODO(hansmuller): remove then after 'Client=' has been removed from Mojom.
+  ProxyProperties.prototype.getLocalDelegate = function() {
+    return this.local && StubBindings(this.local).delegate;
+  }
+
+  // TODO(hansmuller): remove then after 'Client=' has been removed from Mojom.
+  ProxyProperties.prototype.setLocalDelegate = function(impl) {
+    if (this.local)
+      StubBindings(this.local).delegate = impl;
+    else
+      throw new Error("no stub object");
+  }
+
+  ProxyProperties.prototype.close = function() {
+    this.connection.close();
+  }
+
+  // Public stub class properties that are managed at runtime by the JS
+  // bindings. See StubBindings below.
+  function StubProperties(delegate) {
+    this.delegate = delegate;
+  }
+
+  StubProperties.prototype.close = function() {
+    this.connection.close();
+  }
+
+  // The base class for generated proxy classes.
+  function ProxyBase(receiver) {
+    this[kProxyProperties] = new ProxyProperties(receiver);
+
+    // TODO(hansmuller): Temporary, for Chrome backwards compatibility.
+    if (receiver instanceof Router)
+      this.receiver_ = receiver;
+  }
+
+  // The base class for generated stub classes.
+  function StubBase(delegate) {
+    this[kStubProperties] = new StubProperties(delegate);
+  }
+
+  // TODO(hansmuller): remove everything except the connection property doc
+  // after 'Client=' has been removed from Mojom.
+
+  // Provides access to properties added to a proxy object without risking
+  // Mojo interface name collisions. Unless otherwise specified, the initial
+  // value of all properties is undefined.
+  //
+  // ProxyBindings(proxy).connection - The Connection object that links the
+  //   proxy for a remote Mojo service to an optional local stub for a local
+  //   service. The value of ProxyBindings(proxy).connection.remote == proxy.
+  //
+  // ProxyBindings(proxy).local  - The "local" stub object whose delegate
+  //   implements the proxy's Mojo client interface.
+  //
+  // ProxyBindings(proxy).setLocalDelegate(impl) - Sets the implementation
+  //   delegate of the proxy's client stub object. This is just shorthand
+  //   for |StubBindings(ProxyBindings(proxy).local).delegate = impl|.
+  //
+  // ProxyBindings(proxy).getLocalDelegate() - Returns the implementation
+  //   delegate of the proxy's client stub object. This is just shorthand
+  //   for |StubBindings(ProxyBindings(proxy).local).delegate|.
+
+  function ProxyBindings(proxy) {
+    return (proxy instanceof ProxyBase) ? proxy[kProxyProperties] : proxy;
+  }
+
+  // TODO(hansmuller): remove the remote doc after 'Client=' has been
+  // removed from Mojom.
+
+  // Provides access to properties added to a stub object without risking
+  // Mojo interface name collisions. Unless otherwise specified, the initial
+  // value of all properties is undefined.
+  //
+  // StubBindings(stub).delegate - The optional implementation delegate for
+  //  the Mojo interface stub.
+  //
+  // StubBindings(stub).connection - The Connection object that links an
+  //   optional proxy for a remote service to this stub. The value of
+  //   StubBindings(stub).connection.local == stub.
+  //
+  // StubBindings(stub).remote - A proxy for the the stub's Mojo client
+  //   service.
+
+  function StubBindings(stub) {
+    return stub instanceof StubBase ?  stub[kStubProperties] : stub;
+  }
+
   // TODO(hansmuller): the proxy receiver_ property should be receiver$
 
   function BaseConnection(localStub, remoteProxy, router) {
     this.router_ = router;
     this.local = localStub;
     this.remote = remoteProxy;
 
     this.router_.setIncomingReceiver(localStub);
     this.router_.setErrorHandler(function() {
       if (StubBindings(this.local) &&
@@ skipping 147 matching lines @@
   function bindStubDerivedImpl(obj) {
     var pipe = core.createMessagePipe();
     var router = new Router(pipe.handle0);
     var connection = new BaseConnection(obj, undefined, router);
     obj.connection = connection;
     return pipe.handle1;
   }
 
   var exports = {};
   exports.Connection = Connection;
+  exports.EmptyProxy = ProxyBase;
+  exports.EmptyStub = StubBase;
+  exports.ProxyBase = ProxyBase;
+  exports.ProxyBindings = ProxyBindings;
+  exports.StubBase = StubBase;
+  exports.StubBindings = StubBindings;
   exports.TestConnection = TestConnection;
 
   exports.bindProxy = bindProxy;
   exports.getProxy = getProxy;
   exports.bindImpl = bindImpl;
   exports.bindHandleToProxy = bindHandleToProxy;
   exports.bindHandleToStub = bindHandleToStub;
   exports.bindStubDerivedImpl = bindStubDerivedImpl;
   return exports;
 });