A proposal and implementation for an initial postMessage interface. These in...

webkit/plugins/ppapi/ppapi_webplugin_impl.cc

 // Copyright (c) 2010 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.
 
 #include "webkit/plugins/ppapi/ppapi_webplugin_impl.h"
 
 #include <cmath>
 
 #include "base/message_loop.h"
 #include "ppapi/c/pp_var.h"
 #include "third_party/WebKit/Source/WebKit/chromium/public/WebPluginParams.h"
 #include "third_party/WebKit/Source/WebKit/chromium/public/WebPoint.h"
 #include "third_party/WebKit/Source/WebKit/chromium/public/WebRect.h"
 #include "third_party/WebKit/Source/WebKit/chromium/public/WebView.h"
+#include "webkit/plugins/ppapi/message_channel.h"
 #include "webkit/plugins/ppapi/plugin_module.h"
 #include "webkit/plugins/ppapi/ppapi_plugin_instance.h"
 #include "webkit/plugins/ppapi/ppb_url_loader_impl.h"
 #include "webkit/plugins/ppapi/var.h"
 
 using WebKit::WebCanvas;
 using WebKit::WebPluginContainer;
 using WebKit::WebPluginParams;
 using WebKit::WebPoint;
 using WebKit::WebRect;
@@ skipping 58 matching lines @@
     instance_->Delete();
     instance_ = NULL;
   }
 
   MessageLoop::current()->DeleteSoon(FROM_HERE, this);
 }
 
 NPObject* WebPluginImpl::scriptableObject() {
   scoped_refptr<ObjectVar> object(
       ObjectVar::FromPPVar(instance_->GetInstanceObject()));
-  if (object)
-    return object->np_object();
-  return NULL;
+  // If there's an InstanceObject, tell the Instance's MessageChannel to pass
+  // any non-postMessage calls to it.
+  if (object) {
+    instance_->message_channel().set_passthrough_object(
+        object->np_object());
+  }
+  // And return the instance's MessageChannel.
+  return instance_->message_channel().np_object();

[piman, 2011/03/29 04:40:22]

Mmmh.... This CL is causing
http://code.google.com/p/chromium-os/issues/detail?id=13605 to appear.

WebPluginImpl::scriptableObject is supposed to add a refcount to the npobject
(see the NPAPI implementation).

The previous code was wrong, but worked because of 2 bugs and luck:
PluginObject::Create leaks a reference, and this function failed to add one, and
is called only once. It all cancels out.
Unfortunately the new code passes an object on which a reference is never added,
so when the JS engine is done with it and garbage collects it, it destroys it
keeping garbage pointers all around.
Similarly, the instance's object's npobject doesn't get released any more.

 }
 
 void WebPluginImpl::paint(WebCanvas* canvas, const WebRect& rect) {
   if (!instance_->IsFullscreenOrPending())
     instance_->Paint(canvas, plugin_rect_, rect);
 }
 
 void WebPluginImpl::updateGeometry(
     const WebRect& window_rect,
     const WebRect& clip_rect,
@@ skipping 110 matching lines @@
   return instance_->PrintPage(page_number, canvas);
 }
 
 void WebPluginImpl::printEnd() {
   return instance_->PrintEnd();
 }
 
 }  // namespace ppapi
 }  // namespace webkit