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

base/trace_event/process_memory_totals_dump_provider.h

Index: base/trace_event/process_memory_totals_dump_provider.h
diff --git a/base/trace_event/process_memory_totals_dump_provider.h b/base/trace_event/process_memory_totals_dump_provider.h
index 66d4f9956dd5b9144f2352f55209a249e8742017..b443010a49a0903356d4a02c4d4b563ec3f244d5 100644
--- a/base/trace_event/process_memory_totals_dump_provider.h
+++ b/base/trace_event/process_memory_totals_dump_provider.h
@@ -5,6 +5,7 @@
 #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"
@@ -25,6 +26,11 @@ class BASE_EXPORT ProcessMemoryTotalsDumpProvider : public MemoryDumpProvider {
   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);
@@ -36,6 +42,10 @@ class BASE_EXPORT ProcessMemoryTotalsDumpProvider : public MemoryDumpProvider {
 
   scoped_ptr<ProcessMetrics> process_metrics_;
 
+#if defined(OS_LINUX)
+  ScopedFD proc_status_fd_;
+#endif
+
   DISALLOW_COPY_AND_ASSIGN(ProcessMemoryTotalsDumpProvider);
 };