Extract client handing from ChildMemoryCoordinatorImpl

Add ClientRegistry class which becomes a base class of both
MemoryCoordinator and ChildMemoryCoordinatorImpl since client
registration will be the same in both coordinators.

BUG=617492

Review-Url: https://codereview.chromium.org/2144163002
Cr-Commit-Position: refs/heads/master@{#406725}

components/memory_coordinator.gypi

@@ -26,6 +26,8 @@
         'memory_coordinator_mojo_bindings',
       ],
       'sources': [
+        'memory_coordinator/common/client_registry.cc',
+        'memory_coordinator/common/client_registry.h',
         'memory_coordinator/common/memory_coordinator_client.h',
         'memory_coordinator/common/memory_coordinator_features.cc',
         'memory_coordinator/common/memory_coordinator_features.h',

components/memory_coordinator/browser/memory_coordinator.h

@@ -5,6 +5,7 @@
 #ifndef COMPONENTS_MEMORY_COORDINATOR_BROWSER_MEMORY_COORDINATOR_H_
 #define COMPONENTS_MEMORY_COORDINATOR_BROWSER_MEMORY_COORDINATOR_H_
 
+#include "components/memory_coordinator/common/client_registry.h"
 #include "components/memory_coordinator/public/interfaces/memory_coordinator.mojom.h"
 #include "mojo/public/cpp/bindings/binding.h"
 
@@ -15,10 +16,10 @@ class MemoryCoordinatorHandleImpl;
 // MemoryCoordinator is responsible for the whole memory management accross the
 // browser and child proceeses. It will dispatch memory events to its clients
 // and child processes based on its best knowledge of the memory usage.
-class MemoryCoordinator {
+class MemoryCoordinator : public ClientRegistry {
  public:
   MemoryCoordinator();
-  ~MemoryCoordinator();
+  ~MemoryCoordinator() override;
 
   void CreateHandle(int render_process_id,
                     mojom::MemoryCoordinatorHandleRequest request);

components/memory_coordinator/child/child_memory_coordinator_impl.cc

@@ -8,26 +8,16 @@ namespace memory_coordinator {
 
 ChildMemoryCoordinatorImpl::ChildMemoryCoordinatorImpl(
     mojom::MemoryCoordinatorHandlePtr parent)
-    : binding_(this), clients_(new ClientList), parent_(std::move(parent)) {
+    : binding_(this), parent_(std::move(parent)) {
   parent_->AddChild(binding_.CreateInterfacePtrAndBind());
 }
 
 ChildMemoryCoordinatorImpl::~ChildMemoryCoordinatorImpl() {
 }
 
-void ChildMemoryCoordinatorImpl::RegisterClient(
-    MemoryCoordinatorClient* client) {
-  clients_->AddObserver(client);
-}
-
-void ChildMemoryCoordinatorImpl::UnregisterClient(
-    MemoryCoordinatorClient* client) {
-  clients_->RemoveObserver(client);
-}
-
 void ChildMemoryCoordinatorImpl::OnStateChange(mojom::MemoryState state) {
-  clients_->Notify(FROM_HERE, &MemoryCoordinatorClient::OnMemoryStateChange,
-                   state);
+  clients()->Notify(FROM_HERE, &MemoryCoordinatorClient::OnMemoryStateChange,
+                    state);
 }
 
 }  // namespace memory_coordinator

components/memory_coordinator/child/child_memory_coordinator_impl.h

@@ -6,7 +6,7 @@
 #define COMPONENTS_MEMORY_COORDINATOR_CHILD_CHILD_MEMORY_COORDINATOR_IMPL_H_
 
 #include "base/compiler_specific.h"
-#include "base/observer_list_threadsafe.h"
+#include "components/memory_coordinator/common/client_registry.h"
 #include "components/memory_coordinator/common/memory_coordinator_client.h"
 #include "components/memory_coordinator/common/memory_coordinator_features.h"
 #include "components/memory_coordinator/public/interfaces/child_memory_coordinator.mojom.h"
@@ -19,15 +19,12 @@ namespace memory_coordinator {
 // It lives in child processes and is responsible for dispatching memory events
 // to its clients.
 class ChildMemoryCoordinatorImpl
-    : NON_EXPORTED_BASE(public mojom::ChildMemoryCoordinator) {
+    : public ClientRegistry,
+      NON_EXPORTED_BASE(public mojom::ChildMemoryCoordinator) {
  public:
   explicit ChildMemoryCoordinatorImpl(mojom::MemoryCoordinatorHandlePtr parent);
   ~ChildMemoryCoordinatorImpl() override;
 
-  // Registers/unregisters a client. Does not take ownership of client.
-  void RegisterClient(MemoryCoordinatorClient* client);
-  void UnregisterClient(MemoryCoordinatorClient* client);
-
   // mojom::ChildMemoryCoordinator implementations:
   void OnStateChange(mojom::MemoryState state) override;
 
@@ -35,8 +32,6 @@ class ChildMemoryCoordinatorImpl
   friend class ChildMemoryCoordinatorImplTest;
 
   mojo::Binding<mojom::ChildMemoryCoordinator> binding_;
-  using ClientList = base::ObserverListThreadSafe<MemoryCoordinatorClient>;
-  scoped_refptr<ClientList> clients_;
   mojom::MemoryCoordinatorHandlePtr parent_;
 
   DISALLOW_COPY_AND_ASSIGN(ChildMemoryCoordinatorImpl);

components/memory_coordinator/common/BUILD.gn

@@ -4,6 +4,8 @@
 
 source_set("common") {
   sources = [
+    "client_registry.cc",
+    "client_registry.h",
     "memory_coordinator_client.h",
     "memory_coordinator_features.cc",
     "memory_coordinator_features.h",

components/memory_coordinator/common/client_registry.cc

+// 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.
+
+#include "components/memory_coordinator/common/client_registry.h"
+
+namespace memory_coordinator {
+
+ClientRegistry::ClientRegistry() : clients_(new ClientList) {}
+
+ClientRegistry::~ClientRegistry() {}
+
+void ClientRegistry::RegisterClient(MemoryCoordinatorClient* client) {
+  clients_->AddObserver(client);
+}
+
+void ClientRegistry::UnregisterClient(MemoryCoordinatorClient* client) {
+  clients_->RemoveObserver(client);
+}
+
+}  // namespace memory_coordinator

components/memory_coordinator/common/client_registry.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 COMPONENTS_MEMORY_COORDINATOR_COMMON_CLIENT_REGISTRY_H_
+#define COMPONENTS_MEMORY_COORDINATOR_COMMON_CLIENT_REGISTRY_H_
+
+#include "base/observer_list_threadsafe.h"
+#include "components/memory_coordinator/common/memory_coordinator_client.h"
+
+namespace memory_coordinator {
+
+// ClientRegistry is a base class of process-specific memory coordinator
+// and provides ways to register/unregister MemoryCoordinatorClients.
+class ClientRegistry {
+ public:
+  ClientRegistry();
+  virtual ~ClientRegistry();
+
+  // Registers/unregisters a client. Does not take ownership of client.
+  void RegisterClient(MemoryCoordinatorClient* client);
+  void UnregisterClient(MemoryCoordinatorClient* client);
+
+ protected:
+  using ClientList = base::ObserverListThreadSafe<MemoryCoordinatorClient>;
+  ClientList* clients() { return clients_.get(); }
+
+ private:
+  scoped_refptr<ClientList> clients_;
+};
+
+}  // namespace memory_coordinator
+
+#endif  // COMPONENTS_MEMORY_COORDINATOR_COMMON_CLIENT_REGISTRY_H_