Pref service: expose all read-only PrefStores through Mojo

services/preferences/public/cpp/pref_store_manager_impl.cc

+// Copyright 2017 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.
+
+#include "services/preferences/public/cpp/pref_store_manager_impl.h"
+
+#include "base/memory/ref_counted.h"
+#include "components/prefs/pref_value_store.h"
+#include "mojo/public/cpp/bindings/interface_request.h"
+#include "services/service_manager/public/cpp/interface_registry.h"
+
+namespace prefs {
+
+class PrefStoreManagerImpl::ConnectionBarrier

[Sam McNally, 2017/02/24 04:14:53]

Why is this nested?

[tibell, 2017/02/27 00:02:54]

Done.

+    : public base::RefCounted<ConnectionBarrier> {
+ public:
+  ConnectionBarrier(const PrefStorePtrs& pref_store_ptrs,
+                    const ConnectCallback& callback);
+
+ private:
+  friend class base::RefCounted<ConnectionBarrier>;
+  ~ConnectionBarrier();
+
+  void OnConnect(PrefValueStore::PrefStoreType type,
+                 mojom::PrefStoreConnectionPtr connection_ptr);
+
+  ConnectCallback callback_;
+
+  std::unordered_map<PrefValueStore::PrefStoreType,
+                     mojom::PrefStoreConnectionPtr>
+      connections_;
+
+  const size_t expected_connections_;
+
+  DISALLOW_COPY_AND_ASSIGN(ConnectionBarrier);
+};
+
+PrefStoreManagerImpl::ConnectionBarrier::ConnectionBarrier(
+    const PrefStorePtrs& pref_store_ptrs,
+    const ConnectCallback& callback)
+    : callback_(callback), expected_connections_(pref_store_ptrs.size()) {
+  for (const auto& ptr : pref_store_ptrs) {
+    ptr.second->AddObserver(

[Sam McNally, 2017/02/24 04:14:53]

This is perilous if the first ptr is closed. RefCounted starts with a refcount
of 0. The Bind call brings it to 1, and then drops it back to 0, if the pipe is
broken, deleting |this|.

Do this work in a method instead with something external holding a ref.

[tibell, 2017/02/27 00:02:54]

Done.

+        base::Bind(&ConnectionBarrier::OnConnect, this, ptr.first));
+  }
+}
+
+PrefStoreManagerImpl::ConnectionBarrier::~ConnectionBarrier() = default;
+
+// static
+PrefStoreManagerImpl::PrefStoreTypes PrefStoreManagerImpl::DefaultStores() {
+  return {PrefValueStore::MANAGED_STORE};

[Sam McNally, 2017/02/24 04:14:53]

Is this correct?

[tibell, 2017/02/27 00:02:54]

It's temporary in two senses:

1) I'm messing with it while testing the CL.

2) I will fill it out before submitting/final review, but later I believe we'll
instead initialize this somewhere at the Chrome layer and pass the config to the
service in Init.

+}
+
+void PrefStoreManagerImpl::ConnectionBarrier::OnConnect(

[Sam McNally, 2017/02/24 04:14:53]

This should be above DefaultStores().

[tibell, 2017/02/27 00:02:54]

Done.

+    PrefValueStore::PrefStoreType type,
+    mojom::PrefStoreConnectionPtr connection_ptr) {
+  connections_.insert(std::make_pair(type, std::move(connection_ptr)));
+  if (connections_.size() == expected_connections_) {
+    // After this method exits |this| will get destroyed so it's safe to move
+    // out the map.
+    callback_.Run(std::move(connections_));
+  }
+}
+
+PrefStoreManagerImpl::PrefStoreManagerImpl(PrefStoreTypes expected_pref_stores)
+    : expected_pref_stores_(std::move(expected_pref_stores)) {}
+
+PrefStoreManagerImpl::~PrefStoreManagerImpl() = default;
+
+void PrefStoreManagerImpl::Register(mojom::PrefStorePtr pref_store_ptr,
+                                    PrefValueStore::PrefStoreType type) {
+  if (expected_pref_stores_.count(type) == 0) {
+    LOG(WARNING) << "Not registering unexpected pref store: " << type;
+    return;
+  }
+  DVLOG(1) << "Registering pref store: " << type;
+  if (!pref_store_ptrs_.insert(std::make_pair(type, std::move(pref_store_ptr)))
+           .second) {
+    DLOG(FATAL) << "The same pref store registered twice: " << type;
+  }
+  if (AllConnected()) {
+    DVLOG(1) << "All pref stores registered.";
+    if (!pending_callbacks_.empty()) {
+      for (const auto& callback : pending_callbacks_)
+        make_scoped_refptr(new ConnectionBarrier(pref_store_ptrs_, callback));
+      pending_callbacks_.clear();
+    }
+  }
+}
+
+void PrefStoreManagerImpl::Connect(const ConnectCallback& callback) {
+  if (AllConnected())
+    make_scoped_refptr(new ConnectionBarrier(pref_store_ptrs_, callback));
+  else
+    pending_callbacks_.push_back(callback);
+}
+
+void PrefStoreManagerImpl::Create(
+    const service_manager::Identity& remote_identity,
+    prefs::mojom::PrefStoreConnectorRequest request) {
+  connector_bindings_.AddBinding(this, std::move(request));
+}
+
+void PrefStoreManagerImpl::Create(
+    const service_manager::Identity& remote_identity,
+    prefs::mojom::PrefStoreRegistryRequest request) {
+  registry_bindings_.AddBinding(this, std::move(request));
+}
+
+void PrefStoreManagerImpl::OnStart() {}
+
+bool PrefStoreManagerImpl::OnConnect(
+    const service_manager::ServiceInfo& remote_info,
+    service_manager::InterfaceRegistry* registry) {
+  registry->AddInterface<prefs::mojom::PrefStoreConnector>(this);
+  registry->AddInterface<prefs::mojom::PrefStoreRegistry>(this);
+  return true;
+}
+
+bool PrefStoreManagerImpl::AllConnected() const {
+  return pref_store_ptrs_.size() == expected_pref_stores_.size();
+}
+
+}  // namespace prefs