Make DOMWrapperWorld::current() callable from workers

Source/bindings/v8/DOMWrapperWorld.h

Index: Source/bindings/v8/DOMWrapperWorld.h
diff --git a/Source/bindings/v8/DOMWrapperWorld.h b/Source/bindings/v8/DOMWrapperWorld.h
index c95fd0031775f58c53b2c51deeecf54b1a0376b8..69385c1184dc2c3edb715e71a2c20d0b2fab9f92 100644
--- a/Source/bindings/v8/DOMWrapperWorld.h
+++ b/Source/bindings/v8/DOMWrapperWorld.h
@@ -33,6 +33,7 @@
 
 #include "bindings/v8/V8PerContextData.h"
 #include "platform/weborigin/SecurityOrigin.h"
+#include "wtf/MainThread.h"
 #include "wtf/PassRefPtr.h"
 #include "wtf/RefCounted.h"
 #include "wtf/RefPtr.h"
@@ -70,12 +71,28 @@ public:
 
     static DOMWrapperWorld* world(v8::Handle<v8::Context> context)
     {
-        ASSERT(contextHasCorrectPrototype(context));
         return V8PerContextData::world(context);
     }
 
-    // Will return null if there is no DOMWrapperWorld for the current v8::Context
-    static DOMWrapperWorld* current(v8::Isolate*);
+    // Will return null if there is no DOMWrapperWorld for the current context.
+    static DOMWrapperWorld* current(v8::Isolate* isolate)
+    {
+        v8::Handle<v8::Context> context = isolate->GetCurrentContext();
+        if (context.IsEmpty()) {
+            // If a worker thread calls current() with an empty context, it means that there is no DOMWrapperWorld.
+            if (!isMainThread())
+                return 0;
+
+            // If the main thread calls current() with an empty context, it's possible that
+            // current() is being called while window is being initialized.
+            // In order to make current() workable during the initialization phase,
+            // we cache the world of the initializing window on worldOfInitializingWindow.
+            // If there is no initiazing window, worldOfInitializingWindow is 0.
+            return worldOfInitializingWindow;
+        }
+        return world(context);
+    }
+
     static DOMWrapperWorld* mainWorld();
 
     // Associates an isolated world (see above for description) with a security
@@ -105,11 +122,19 @@ public:
     int extensionGroup() const { return m_extensionGroup; }
     DOMDataStore& domDataStore() { return *m_domDataStore; }
 
-private:
-    static unsigned isolatedWorldCount;
+    static void setWorldOfInitializingWindow(DOMWrapperWorld* world)
+    {
+        ASSERT(isMainThread());
+        worldOfInitializingWindow = world;
+    }
+    // FIXME: Remove this method once we fix crbug.com/345014.
+    static bool windowIsBeingInitialized() { return !!worldOfInitializingWindow; }
 
+private:
     DOMWrapperWorld(int worldId, int extensionGroup);
-    static bool contextHasCorrectPrototype(v8::Handle<v8::Context>);
+
+    static unsigned isolatedWorldCount;
+    static DOMWrapperWorld* worldOfInitializingWindow;
 
     const int m_worldId;
     const int m_extensionGroup;