[Oilpan] Unify memory usage reporters of Oilpan

third_party/WebKit/Source/platform/MemoryUsageProvider.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 MemoryUsageProvider_h
+#define MemoryUsageProvider_h
+
+#include "public/platform/WebCommon.h"
+#include "public/platform/WebMemoryDumpProvider.h"
+#include "wtf/Allocator.h"
+#include "wtf/Noncopyable.h"
+
+namespace v8 {
+class Isolate;
+}
+
+namespace blink {
+
+class MemoryUsageProvider {
+    USING_FAST_MALLOC(MemoryUsageProvider);
+    WTF_MAKE_NONCOPYABLE(MemoryUsageProvider);
+public:
+    // Returns a thread specific instance.
+    static MemoryUsageProvider* instance();
+
+    MemoryUsageProvider();
+    ~MemoryUsageProvider();
+
+    void setIsolate(v8::Isolate* isolate) { m_isolate = isolate; }
+
+    // Returns if it reported the memory usage.
+    bool adjustAmountOfAllocatedMemory();
+
+private:
+    v8::Isolate* m_isolate;
+    int64_t m_previousSize;
+};
+
+} // namespace blink
+
+#endif // PartitionAllocMemoryDumpProvider_h