Some fleshing out the mojo based localstorage implementation.

content/browser/leveldb_wrapper_impl.h

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CONTENT_BROWSER_LEVELDB_WRAPPER_IMPL_H_
 #define CONTENT_BROWSER_LEVELDB_WRAPPER_IMPL_H_
 
 #include "base/callback.h"
 #include "base/macros.h"
 #include "content/common/leveldb_wrapper.mojom.h"
 #include "mojo/public/cpp/bindings/binding_set.h"
+#include "mojo/public/cpp/bindings/interface_ptr_set.h"
 
 namespace content {
 
 // This is a wrapper around a leveldb::LevelDBDatabase. It adds a couple of
 // features:
 // 1) Adds the given prefix, if any, to all keys. This allows the sharing of one
 //    database across many, possibly untrusted, consumers and ensuring that they
 //    can't access each other's values.
-// 2) Informs an observer when the given prefix' values are modified by another
-//    process.
-// 3) Throttles requests to avoid overwhelming the disk.
+// 2) Enforces a max_size constraint.
+// 3) Informs an observer when the given prefix' values are modified.
+// 4) Throttles requests to avoid overwhelming the disk.
 class LevelDBWrapperImpl : public mojom::LevelDBWrapper {
  public:
   // |no_bindings_callback| will be called when this object has no more
   // bindings.
   LevelDBWrapperImpl(leveldb::LevelDBDatabase* database,
                      const std::string& prefix,
+                     size_t max_size,
                      const base::Closure& no_bindings_callback);
   ~LevelDBWrapperImpl() override;
 
   void Bind(mojom::LevelDBWrapperRequest request);
+  void AddObserver(mojom::LevelDBObserverPtr observer);
 
  private:
   // LevelDBWrapperImpl:
   void Put(mojo::Array<uint8_t> key,
            mojo::Array<uint8_t> value,
            const mojo::String& source,
            const PutCallback& callback) override;
   void Delete(mojo::Array<uint8_t> key,
               const mojo::String& source,
               const DeleteCallback& callback) override;
-  void DeleteAll(mojom::LevelDBObserverPtr observer,
-                 const mojo::String& source,
+  void DeleteAll(const mojo::String& source,
                  const DeleteAllCallback& callback) override;
   void Get(mojo::Array<uint8_t> key, const GetCallback& callback) override;
-  void GetAll(mojom::LevelDBObserverPtr observer,
+  void GetAll(const mojo::String& source,
               const GetAllCallback& callback) override;
 
   void OnConnectionError();
 
   std::string prefix_;
   mojo::BindingSet<mojom::LevelDBWrapper> bindings_;
+  mojo::InterfacePtrSet<mojom::LevelDBObserver> observers_;
   base::Closure no_bindings_callback_;
   leveldb::LevelDBDatabase* database_;
+  std::map<mojo::Array<uint8_t>, mojo::Array<uint8_t>> map_;
+  size_t bytes_used_;
+  size_t max_size_;
 
   DISALLOW_COPY_AND_ASSIGN(LevelDBWrapperImpl);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_LEVELDB_WRAPPER_IMPL_H_