[ABANDONED] Introduce Promise example implementation written in JavaScript.

Source/core/dom/Promise.js

Index: Source/core/dom/Promise.js
diff --git a/Source/core/platform/Task.h b/Source/core/dom/Promise.js
similarity index 80%
copy from Source/core/platform/Task.h
copy to Source/core/dom/Promise.js
index b9d2e46802aebf6391df4ec3dabb580d43b2483c..26562d4298b2f85b6650de9dc4d2490f2665e798 100644
--- a/Source/core/platform/Task.h
+++ b/Source/core/dom/Promise.js
@@ -28,30 +28,27 @@
  * 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;
-};
-
-} // namespace WebCore
+    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.

+    }
 
-#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]

+});