[ABANDONED] Introduce Promise example implementation written in JavaScript.

Source/core/dom/Promise.js

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 10 matching lines @@
  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
-#ifndef Task_h
-#define Task_h
-
-#include "wtf/Functional.h"
-#include "public/platform/WebThread.h"
-
-namespace WebCore {
-
-class Task : public WebKit::WebThread::Task {
-public:
-    explicit Task(const Closure& closure)
-        : m_closure(closure)
+(function() {
+    function get(value)
     {
+        var old = this.value;
+        this.value = value;
+        return old;
     }
 
-    virtual void run() OVERRIDE
+    function getStatic(value)
     {
-        m_closure();
+        return new Promise(value);

[abarth-chromium, 2013/06/18 09:17:22]

This calls whatever the web page has mutated window.Promise to be.  Instead, we
need to call $Promise here.

[yhirano, 2013/06/19 12:55:56]

Done. Please see Promise-overwrite-constructor.html.

     }
 
-private:
-    Closure m_closure;
-};
+    function $Promise(value)
+    {
+        this.value = value;

[abarth-chromium, 2013/06/18 09:13:16]

I'm worried that this will call setters on Object.prototype.  Consider if the
page does the following:

Object.prototype.__defineSetter__("value", function() { alert("hacked") });
var p = new Promise();

Won't that trigger the alert?

[yhirano, 2013/06/19 12:55:56]

Done. Please see Promise-define-setter.html.

+    }
 
-} // namespace WebCore
-
-#endif // Task_h
+    $Promise.prototype = {

[jsbell, 2013/06/18 18:23:13]

Possibly use $Promise.prototype = Object.create(null, descriptor); here - you're
probably going to want to configure the properties anyway.

[abarth-chromium, 2013/06/18 18:41:35]

Both Object and create would be external dependencies...

I'm starting to think we need to investigate a different approach.  It's too
hard to avoid all dependencies on the page's JS environment.

[jsbell, 2013/06/18 19:00:08]

If this is run *after* user scripts can touch the page, yes. The SES folks would
probably say that if you aren't the first script on the page you there is very
little you can assert about the behavior of your script.

(That may be what you mean by "different approach".)

[yhirano, 2013/06/19 12:55:56]

There is no external dependencies now.
No property customize is needed, since Web developers can't access this object
directly.

+        get: get
+    };
+    $Promise.getStatic = getStatic;
+    return $Promise;

[abarth-chromium, 2013/06/18 09:17:22]

What does this print:

console.log((new Promise(42)).toString())

?

[yhirano, 2013/06/19 12:55:56]

[object Promise]

+});