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 4b9d597b145adc29ed8c8b965f3111df689daf81..417061cf7b7dd110c0725bbd42919e0c14d71f1f 100644
--- a/Source/core/html/HTMLPlugInElement.cpp
+++ b/Source/core/html/HTMLPlugInElement.cpp
@@ -86,9 +86,50 @@ 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) {
+        m_persistedPluginWidget->dispose();
+        m_persistedPluginWidget = nullptr;
+    }
+    HTMLFrameOwnerElement::disconnectContentFrame();
+}
+
+void HTMLPlugInElement::setIsAllowedToDisposePlugin()

[haraken, 2014/10/10 02:50:32]

setIsAllowedToDisposePlugin => shouldDisposePlugin ?

[sof, 2014/10/10 08:40:55]

That's a better verb to use, thanks. disposal isn't optional.

+{
+    if (m_persistedPluginWidget && m_persistedPluginWidget->isPluginView()) {
+        PluginView* plugin = toPluginView(m_persistedPluginWidget.get());
+        plugin->setIsAllowedToDisposePlugin();
+    }
+}
+#endif
+
+void HTMLPlugInElement::setPersistedPluginWidget(Widget* widget)
+{
+#if ENABLE(OILPAN)
+    if (m_persistedPluginWidget && m_persistedPluginWidget != widget) {
+        if (m_persistedPluginWidget->isPluginView()) {
+            PluginView* oldPlugin = toPluginView(m_persistedPluginWidget.get());
+            if (LocalFrame* frame = oldPlugin->pluginFrame()) {

[haraken, 2014/10/10 02:50:32]

Help me understand: In a case where oldPlugin->pluginFrame() returns 0, who
called dispose() for the plugin? I'm curious how it's guaranteed that dispose()
is always called for all plugins.

[sof, 2014/10/10 05:22:19]

The condition cannot happen (see below.)

+                frame->unregisterPluginElement(this);
+            }
+        }
+    }
+    if (widget && widget->isPluginView()) {
+        PluginView* plugin = toPluginView(widget);
+        if (LocalFrame* frame = plugin->pluginFrame()) {

[haraken, 2014/10/10 02:50:32]

Help me understand: Who calls dispose() for a plugin if plugin->pluginFrame()
returns 0 (and thus we fail to register the plugin to the frame) ?

[sof, 2014/10/10 05:22:18]

I don't think any such plugins exist. i.e., WebPluginContainerImpl is the only
implementation of PluginView and it always has a Frame (at least when in this
method.)

+            frame->registerPluginElement(this);
+        }
+    }
+#endif
+    m_persistedPluginWidget = widget;
+}
+
 bool HTMLPlugInElement::canProcessDrag() const
 {
     return pluginWidget() && pluginWidget()->isPluginView() && toPluginView(pluginWidget())->canProcessDrag();
@@ -201,13 +242,10 @@ void HTMLPlugInElement::detach(const AttachContext& context)
     // Only try to persist a plugin widget we actually own.
     Widget* plugin = ownedWidget();
     if (plugin && plugin->pluginShouldPersist())
-        m_persistedPluginWidget = plugin;
-#if ENABLE(OILPAN)
-    else if (plugin)
-        plugin->detach();
-#endif
+        setPersistedPluginWidget(plugin);
+
     resetInstance();
-    // FIXME - is this next line necessary?
+    // Clear the widget; will trigger disposal of it with Oilpan.
     setWidget(nullptr);
 
     if (m_isCapturingMouseEvents) {
@@ -335,7 +373,7 @@ 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);
@@ -478,7 +516,7 @@ 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;
@@ -493,9 +531,9 @@ bool HTMLPlugInElement::loadPlugin(const KURL& url, const String& mimeType, cons
 
     if (renderer) {
         setWidget(widget);
-        m_persistedPluginWidget = nullptr;
+        setPersistedPluginWidget(nullptr);
     } else if (widget != m_persistedPluginWidget) {
-        m_persistedPluginWidget = widget;
+        setPersistedPluginWidget(widget.get());
     }
     document().setContainsPlugins();
     scheduleSVGFilterLayerUpdateHack();