[tracing] Send smaps file desciptor to child process for tracing

base/trace_event/process_memory_totals_dump_provider.h

 // 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 BASE_TRACE_EVENT_PROCESS_MEMORY_TOTALS_DUMP_PROVIDER_H_
 #define BASE_TRACE_EVENT_PROCESS_MEMORY_TOTALS_DUMP_PROVIDER_H_
 
+#include "base/files/scoped_file.h"
 #include "base/gtest_prod_util.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/singleton.h"
 #include "base/trace_event/memory_dump_provider.h"
 
 namespace base {
 
 class ProcessMetrics;
 
 namespace trace_event {
 
 // Dump provider which collects process-wide memory stats.
 class BASE_EXPORT ProcessMemoryTotalsDumpProvider : public MemoryDumpProvider {
  public:
   static ProcessMemoryTotalsDumpProvider* GetInstance();
 
   // MemoryDumpProvider implementation.
   bool OnMemoryDump(const MemoryDumpArgs& args,
                     ProcessMemoryDump* pmd) override;
 
+#if defined(OS_LINUX)
+  void set_proc_status_fd(int fd) { proc_status_fd_.reset(fd); }
+  void reset_proc_status_fd() { proc_status_fd_.reset(); }
+#endif
+
  private:
   friend struct DefaultSingletonTraits<ProcessMemoryTotalsDumpProvider>;
   FRIEND_TEST_ALL_PREFIXES(ProcessMemoryTotalsDumpProviderTest, DumpRSS);
 
   static uint64 rss_bytes_for_testing;
 
   ProcessMemoryTotalsDumpProvider();
   ~ProcessMemoryTotalsDumpProvider() override;
 
   scoped_ptr<ProcessMetrics> process_metrics_;
 
+#if defined(OS_LINUX)
+  ScopedFD proc_status_fd_;
+#endif
+
   DISALLOW_COPY_AND_ASSIGN(ProcessMemoryTotalsDumpProvider);
 };
 
 }  // namespace trace_event
 }  // namespace base
 
 #endif  // BASE_TRACE_EVENT_PROCESS_MEMORY_TOTALS_DUMP_PROVIDER_H_