Implement throttling behavior for LocalStorage mojo messages.

content/browser/leveldb_wrapper_impl.cc

Index: content/browser/leveldb_wrapper_impl.cc
diff --git a/content/browser/leveldb_wrapper_impl.cc b/content/browser/leveldb_wrapper_impl.cc
index 6ec51c70862c569e9e5db571bde7a3c73bcf338c..97c793ed6c6daeebca97c89de5efe69a43e6e359 100644
--- a/content/browser/leveldb_wrapper_impl.cc
+++ b/content/browser/leveldb_wrapper_impl.cc
@@ -244,6 +244,10 @@ void LevelDBWrapperImpl::GetAll(
   }
 }
 
+void LevelDBWrapperImpl::FlushPipe(const FlushPipeCallback& callback) {
+  callback.Run();
+}
+
 void LevelDBWrapperImpl::OnConnectionError() {
   if (!bindings_.empty())
     return;