Reland: Add MemoryCoordinatorClient

third_party/WebKit/Source/platform/MemoryCoordinator.h

Index: third_party/WebKit/Source/platform/MemoryCoordinator.h
diff --git a/third_party/WebKit/Source/platform/MemoryCoordinator.h b/third_party/WebKit/Source/platform/MemoryCoordinator.h
new file mode 100644
index 0000000000000000000000000000000000000000..fd540de3920f2c6a548c04b7b1c5a4e5edf327e2
--- /dev/null
+++ b/third_party/WebKit/Source/platform/MemoryCoordinator.h
@@ -0,0 +1,53 @@
+// Copyright 2015 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 MemoryCoordinator_h
+#define MemoryCoordinator_h
+
+#include "platform/PlatformExport.h"
+#include "platform/heap/Handle.h"
+#include "public/platform/WebMemoryPressureLevel.h"
+#include "wtf/Noncopyable.h"
+
+namespace blink {
+
+class PLATFORM_EXPORT MemoryCoordinatorClient : public GarbageCollectedMixin {
+public:
+    virtual ~MemoryCoordinatorClient() { }
+
+    // Called when MemoryCoordinator is asked to purge memory.
+    virtual void purgeMemory() { }
+
+    // TODO(bashi): Deprecating. Remove this when MemoryPressureListener is
+    // gone.
+    virtual void onMemoryPressure(WebMemoryPressureLevel) { }
+};
+
+// MemoryCoordinator listens to some events which could be opportunities
+// for reducing memory consumption and notifies its clients.
+class PLATFORM_EXPORT MemoryCoordinator final : public GarbageCollected<MemoryCoordinator> {
+    WTF_MAKE_NONCOPYABLE(MemoryCoordinator);
+public:
+    static MemoryCoordinator& instance();
+
+    void registerClient(MemoryCoordinatorClient*);
+    void unregisterClient(MemoryCoordinatorClient*);
+
+    void purgeMemory();
+
+    // TODO(bashi): Deprecating. Remove this when MemoryPressureListener is
+    // gone.
+    void onMemoryPressure(WebMemoryPressureLevel);
+
+    DECLARE_TRACE();
+
+private:
+    MemoryCoordinator();
+
+    HeapHashSet<WeakMember<MemoryCoordinatorClient>> m_clients;
+};
+
+} // namespace blink
+
+#endif // MemoryCoordinator_h