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 eb8cd427cbc3e215630590909f6982a5470b3e77..8b17cb2f93753940a369aa9022f1cf7e766c377a 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);