Add UMA for PurgeAndSuspend.

third_party/WebKit/public/web/WebMemoryStatistics.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 WebMemoryStatistics_h
+#define WebMemoryStatistics_h
+
+#include "public/platform/WebCommon.h"
+
+namespace blink {
+
+struct WebMemoryStatistics {
+  size_t partitionAllocTotalAllocatedBytes;
+  size_t blinkGCTotalAllocatedBytes;
+
+  WebMemoryStatistics()
+      : partitionAllocTotalAllocatedBytes(0), blinkGCTotalAllocatedBytes(0) {}
+
+  BLINK_EXPORT static WebMemoryStatistics Get();
+};
+
+}  // namespace blink
+
+#endif