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

public/platform/WebMemoryDumpProvider.h

Index: public/platform/WebMemoryDumpProvider.h
diff --git a/public/platform/WebMemoryDumpProvider.h b/public/platform/WebMemoryDumpProvider.h
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+++ b/public/platform/WebMemoryDumpProvider.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 WebMemoryDumpProvider_h
+#define WebMemoryDumpProvider_h
+
+#include "WebNonCopyable.h"
+
+namespace blink {
+
+class WebProcessMemoryDump;
+
+// Base interface to be part of the memory tracing infrastructure. Blink classes
+// can implement this interface and register themselves (see
+// Platform::registerMemoryDumpProvider()) to dump stats for their allocators.
+class BLINK_PLATFORM_EXPORT WebMemoryDumpProvider {
+public:
+    // Called by the MemoryDumpManager when generating memory dumps. Embedders
+    // are expected to populate the WebProcessMemoryDump* argument and return
+    // true on success or false if anything went wrong and the dump should be
+    // considered invalid.
+    virtual bool onMemoryDump(WebProcessMemoryDump*) = 0;
+};
+
+} // namespace blink
+
+#endif // WebMemoryDumpProvider_h