Create and use BlinkInterfaceProvider WeakPtrs on the same thread

content/renderer/mojo/blink_interface_provider_impl.h

Index: content/renderer/mojo/blink_interface_provider_impl.h
diff --git a/content/renderer/mojo/blink_interface_provider_impl.h b/content/renderer/mojo/blink_interface_provider_impl.h
index 4fd4a66c822652b5ddf742c26aa53ebdb2b30638..49322c739da6726ad92a4c905cf8e4e82704d5fb 100644
--- a/content/renderer/mojo/blink_interface_provider_impl.h
+++ b/content/renderer/mojo/blink_interface_provider_impl.h
@@ -38,6 +38,9 @@ class BlinkInterfaceProviderImpl : public blink::InterfaceProvider {
 
   scoped_refptr<base::SingleThreadTaskRunner> main_thread_task_runner_;
 
+  // Should only be accessed by Web Worker threads that are using the
+  // blink::Platform-level interface provider.
+  base::WeakPtr<BlinkInterfaceProviderImpl> weak_ptr_;
   base::WeakPtrFactory<BlinkInterfaceProviderImpl> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(BlinkInterfaceProviderImpl);