[tracing] Expose memory-infra tracing infrastructure to Blink.

public/platform/WebMemoryAllocatorDump.h

Index: public/platform/WebMemoryAllocatorDump.h
diff --git a/public/platform/WebMemoryAllocatorDump.h b/public/platform/WebMemoryAllocatorDump.h
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+++ b/public/platform/WebMemoryAllocatorDump.h
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+// 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 WebMemoryAllocatorDump_h
+#define WebMemoryAllocatorDump_h
+
+#include "WebCommon.h"
+#include "WebNonCopyable.h"
+#include "WebString.h"
+
+namespace blink {
+
+// A container which holds all the attributes of a particular dump for a given
+// allocator.
+class BLINK_PLATFORM_EXPORT WebMemoryAllocatorDump : public WebNonCopyable {
+public:
+    // Adds a scalar attribute to the dump.
+    // Arguments:
+    //   name: name of the attribute. Typical names, emitted by most allocators
+    //       dump providers are: "outer_size", "inner_size", "objects_count".
+    //   units: the units for the attribute. Gives a hint to the trace-viewer UI
+    //       about the semantics of the attribute.
+    //       Currently supported values are "bytes" and "objects".
+    //   value: the value of the attribute.
+    virtual void AddScalar(const WebString& name, const char* units, uint64_t value) { }
+    virtual void AddString(const WebString& name, const char* units, const WebString& value) { }
+};
+
+} // namespace blink
+
+#endif // WebMemoryAllocatorDump_h