Move the Widget hierarchy to the Oilpan heap.

Source/core/html/HTMLPlugInElement.cpp

Index: Source/core/html/HTMLPlugInElement.cpp
diff --git a/Source/core/html/HTMLPlugInElement.cpp b/Source/core/html/HTMLPlugInElement.cpp
index 92f848045731df1a2697ca41d9ec4eea1309df66..7efed677a229d8b4254cc5e6c0591b51667aaf0b 100644
--- a/Source/core/html/HTMLPlugInElement.cpp
+++ b/Source/core/html/HTMLPlugInElement.cpp
@@ -78,6 +78,11 @@ HTMLPlugInElement::~HTMLPlugInElement()
     ASSERT(!m_pluginWrapper); // cleared in detach()
     ASSERT(!m_isDelayingLoadEvent);
 
+#if ENABLE(OILPAN)
+    if (m_persistedPluginWidget)
+        HTMLFrameOwnerElement::disposeWidget(m_persistedPluginWidget.get());

[haraken, 2014/09/29 14:16:36]

Can't we call HTMLFrameOwnerElement::disposeWidget when the HTMLPlugInElement is
removed from the DOM tree?

Ideally we want to call disposeWidget in HTMLPlugInElement::removedFrom() if the
Widget dies before the HTMLPlugInElement, and don't call anything if the Widget
and the HTMLPlugInElement die together.

Then we want to make m_persistedPluginWidget a Member<Widget>.

I wonder what prevents us from doing something like that.

[sof, 2014/10/07 13:27:32]

That the plugin element isn't in the tree to start with :-) i.e., we can create
a plugin element outside the tree and load a renderer-less plugin.

See plugins/can-create-without-renderer.html for an example.

The disposal steps you refer to is set up to happen here in this CL if the
plugin element is attached to tree, I think (see
HTMLPlugInElement::disconnectContentFrame().)

+#endif
+
     if (m_NPObject) {
         _NPN_ReleaseObject(m_NPObject);
         m_NPObject = 0;
@@ -87,9 +92,19 @@ HTMLPlugInElement::~HTMLPlugInElement()
 void HTMLPlugInElement::trace(Visitor* visitor)
 {
     visitor->trace(m_imageLoader);
+    visitor->trace(m_persistedPluginWidget);
     HTMLFrameOwnerElement::trace(visitor);
 }
 
+#if ENABLE(OILPAN)
+void HTMLPlugInElement::disconnectContentFrame()
+{
+    if (m_persistedPluginWidget)
+        HTMLFrameOwnerElement::disposeWidget(m_persistedPluginWidget.get());
+    HTMLFrameOwnerElement::disconnectContentFrame();
+}
+#endif
+
 bool HTMLPlugInElement::canProcessDrag() const
 {
     return pluginWidget() && pluginWidget()->isPluginView() && toPluginView(pluginWidget())->canProcessDrag();
@@ -343,7 +358,7 @@ void HTMLPlugInElement::defaultEventHandler(Event* event)
         if (toRenderEmbeddedObject(r)->showsUnavailablePluginIndicator())
             return;
     }
-    RefPtr<Widget> widget = toRenderWidget(r)->widget();
+    RefPtrWillBeRawPtr<Widget> widget = toRenderWidget(r)->widget();
     if (!widget)
         return;
     widget->handleEvent(event);
@@ -483,7 +498,7 @@ bool HTMLPlugInElement::loadPlugin(const KURL& url, const String& mimeType, cons
     WTF_LOG(Plugins, "   Loaded URL: %s", url.string().utf8().data());
     m_loadedUrl = url;
 
-    RefPtr<Widget> widget = m_persistedPluginWidget;
+    RefPtrWillBeRawPtr<Widget> widget = m_persistedPluginWidget;
     if (!widget) {
         bool loadManually = document().isPluginDocument() && !document().containsPlugins();
         FrameLoaderClient::DetachedPluginPolicy policy = requireRenderer ? FrameLoaderClient::FailOnDetachedPlugin : FrameLoaderClient::AllowDetachedPlugin;