Implement throttling behavior for LocalStorage mojo messages.

content/browser/leveldb_wrapper_impl.h

Index: content/browser/leveldb_wrapper_impl.h
diff --git a/content/browser/leveldb_wrapper_impl.h b/content/browser/leveldb_wrapper_impl.h
index 96988329725e31dc5abab8747ee39918a8058312..696700f152bbf4c3e769da7bf5bbbeb62c3bc1d7 100644
--- a/content/browser/leveldb_wrapper_impl.h
+++ b/content/browser/leveldb_wrapper_impl.h
@@ -80,6 +80,7 @@ class CONTENT_EXPORT LevelDBWrapperImpl : public mojom::LevelDBWrapper {
   void GetAll(
       mojom::LevelDBWrapperGetAllCallbackAssociatedPtrInfo complete_callback,
       const GetAllCallback& callback) override;
+  void FlushPipe(const FlushPipeCallback& callback) override;
 
  private:
   using ValueMap = std::map<std::vector<uint8_t>, std::vector<uint8_t>>;