Make sure the plugin scriptable object is released before NPP_Destroy.

When the we tear down a plugin instance the plugin process first invokes NPP_Destroy, and then tears down the IPC channel to the renderer, to give NPP_Destroy a chance to do last-minute scripting.  When the IPC channel for the last instance is torn down we also clean up the IPC channels and stubs for any plugin-side NPObjects that remain.

We suspect that some plugins implement the scriptable object as part of the plugin instance, rather than independently ref-counted, so that our releasing the object after NPP_Destroy actually triggers the plugin process to crash.

This CL tears down the stub for the plugin's scriptable object before we call NPP_Destroy.

As per crbug.com/119414, we will remove this code if it doesn't significantly impact crashes.

BUG=101968

Review URL: http://codereview.chromium.org/9817023

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@128179 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 19 insertions, 8 deletions

diff --git a/content/plugin/webplugin_delegate_stub.cc b/content/plugin/webplugin_delegate_stub.cc
index bc130b2..c74f07b1 100644
--- a/content/plugin/webplugin_delegate_stub.cc
+++ b/content/plugin/webplugin_delegate_stub.cc
@@ -9,7 +9,6 @@
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/string_number_conversions.h"
-#include "content/common/npobject_stub.h"
 #include "content/common/plugin_messages.h"
 #include "content/plugin/plugin_channel.h"
 #include "content/plugin/plugin_thread.h"
@@ -31,7 +30,13 @@ using webkit::npapi::WebPlugin;
 using webkit::npapi::WebPluginResourceClient;
 
 static void DestroyWebPluginAndDelegate(
-    webkit::npapi::WebPluginDelegateImpl* delegate, WebPlugin* webplugin) {
+    base::WeakPtr<NPObjectStub> scriptable_object,
+    webkit::npapi::WebPluginDelegateImpl* delegate,
+    WebPlugin* webplugin) {
+  // The plugin may not expect us to try to release the scriptable object
+  // after calling NPP_Destroy on the instance, so delete the stub now.
+  if (scriptable_object.get())
+    scriptable_object->DeleteSoon();
   // WebPlugin must outlive WebPluginDelegate.
   if (delegate)
     delegate->PluginDestroyed();
@@ -58,10 +63,12 @@ WebPluginDelegateStub::~WebPluginDelegateStub() {
     // The delegate or an npobject is in the callstack, so don't delete it
     // right away.
     MessageLoop::current()->PostNonNestableTask(FROM_HERE,
-        base::Bind(&DestroyWebPluginAndDelegate, delegate_, webplugin_));
+        base::Bind(&DestroyWebPluginAndDelegate, plugin_scriptable_object_,
+                   delegate_, webplugin_));
   } else {
     // Safe to delete right away.
-    DestroyWebPluginAndDelegate(delegate_, webplugin_);
+    DestroyWebPluginAndDelegate(
+        plugin_scriptable_object_, delegate_, webplugin_);
   }
 }
 
@@ -282,11 +289,13 @@ void WebPluginDelegateStub::OnGetPluginScriptableObject(int* route_id) {
   }
 
   *route_id = channel_->GenerateRouteID();
-  // The stub will delete itself when the proxy tells it that it's released, or
-  // otherwise when the channel is closed.
-  new NPObjectStub(
+  // We will delete the stub immediately before calling PluginDestroyed on the
+  // delegate. It will delete itself sooner if the proxy tells it that it has
+  // been released, or if the channel to the proxy is closed.
+  NPObjectStub* scriptable_stub = new NPObjectStub(
       object, channel_.get(), *route_id, webplugin_->containing_window(),
       page_url_);
+  plugin_scriptable_object_ = scriptable_stub->AsWeakPtr();
 
   // Release ref added by GetPluginScriptableObject (our stub holds its own).
   WebBindings::releaseObject(object);
diff --git a/content/plugin/webplugin_delegate_stub.h b/content/plugin/webplugin_delegate_stub.h
index 8d7d3df..deddd49 100644
--- a/content/plugin/webplugin_delegate_stub.h
+++ b/content/plugin/webplugin_delegate_stub.h
@@ -1,4 +1,4 @@
-// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Copyright (c) 2012 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.
 
@@ -10,6 +10,7 @@
 #include <vector>
 
 #include "base/memory/ref_counted.h"
+#include "content/common/npobject_stub.h"
 #include "googleurl/src/gurl.h"
 #include "ipc/ipc_channel.h"
 #include "third_party/npapi/bindings/npapi.h"
@@ -113,6 +114,7 @@ class WebPluginDelegateStub : public IPC::Channel::Listener,
 
   scoped_refptr<PluginChannel> channel_;
 
+  base::WeakPtr<NPObjectStub> plugin_scriptable_object_;
   webkit::npapi::WebPluginDelegateImpl* delegate_;
   WebPluginProxy* webplugin_;
   bool in_destructor_;