[WIP] Add SharedMemoryTracker to dump base::SharedMemory usage

base/memory/shared_memory_dump_provider.cc

+// 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.
+
+#include "base/memory/shared_memory_dump_provider.h"
+
+#include "base/threading/thread_task_runner_handle.h"
+#include "base/trace_event/memory_dump_manager.h"
+#include "base/trace_event/process_memory_dump.h"
+
+namespace base {
+
+SharedMemoryDumpProvider* SharedMemoryDumpProvider::GetInstance() {
+  return base::Singleton<
+      SharedMemoryDumpProvider,
+      base::LeakySingletonTraits<SharedMemoryDumpProvider>>::get();
+}
+
+bool SharedMemoryDumpProvider::OnMemoryDump(
+    const base::trace_event::MemoryDumpArgs& args,
+    base::trace_event::ProcessMemoryDump* pmd) {
+  base::trace_event::MemoryAllocatorDump* dump =
+      pmd->CreateAllocatorDump("shared");
+  dump->AddScalar(base::trace_event::MemoryAllocatorDump::kNameSize,
+                  base::trace_event::MemoryAllocatorDump::kUnitsBytes,
+                  total_memory_usage_);
+  return true;
+}
+
+void SharedMemoryDumpProvider::AddSuballocation(
+    trace_event::ProcessMemoryDump* pmd,
+    const trace_event::MemoryAllocatorDumpGuid& source) {
+  pmd->AddSuballocation(source, "shared");
+}
+
+SharedMemoryDumpProvider::SharedMemoryDumpProvider() {
+  base::trace_event::MemoryDumpManager::GetInstance()->RegisterDumpProvider(
+      this, "SharedMemoryDumpProvider", base::ThreadTaskRunnerHandle::Get());
+}
+
+SharedMemoryDumpProvider::~SharedMemoryDumpProvider() {}
+
+}  // namespace