Oilpan: fix build after r190700 (99fb464b7).

Source/web/WebPluginContainerImpl.cpp

Index: Source/web/WebPluginContainerImpl.cpp
diff --git a/Source/web/WebPluginContainerImpl.cpp b/Source/web/WebPluginContainerImpl.cpp
index 9c4b46251b5752f8d3c15b0d8179526976f0f12f..ab3a47e8f97dd029fd461b7cd06905dc06dd83b7 100644
--- a/Source/web/WebPluginContainerImpl.cpp
+++ b/Source/web/WebPluginContainerImpl.cpp
@@ -597,14 +597,19 @@ v8::Local<v8::Object> WebPluginContainerImpl::scriptableObject(v8::Isolate* isol
 {
     // The plugin may be destroyed due to re-entrancy when calling
     // v8ScriptableObject below. crbug.com/458776. Hold a reference to the
-    // plugin container to prevent this from happening.
+    // plugin container to prevent this from happening. For Oilpan, 'this'
+    // is already stack reachable, so redundant.
     RefPtrWillBeRawPtr<WebPluginContainerImpl> protector(this);
 
     v8::Local<v8::Object> object = m_webPlugin->v8ScriptableObject(isolate);
 
     // If the plugin has been destroyed and the reference on the stack is the
     // only one left, then don't return the scriptable object.
+#if ENABLE(OILPAN)
+    if (!m_webPlugin)

[raymes, 2015/02/24 23:55:26]

Hmm I don't really understand what the problem was here. Could you explain more?
Why does hasOneRef not work (sorry I have no idea what oilpan is!)

In this case we were trying to avoid calling into the plugin if it is about to
be destroyed which seems wise.

[raymes, 2015/02/24 23:59:29]

Actually I think this seems reasonable as it looks like in the case of oilpan
it's possible the plugin may have been destroyed in the re-entrant call.

Thanks!

[sof, 2015/02/25 07:04:49]

If it ends up being disposed of, m_webPlugin will be cleared.

This container object itself cannot be destructed as it is on the Oilpan heap,
so if a garbage collection should strike across that troublesome call, the
object will be kept alive as the stack refers to it.

+#else
     if (hasOneRef())
+#endif
         return v8::Local<v8::Object>();
 
     if (!object.IsEmpty()) {