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

base/trace_event/process_memory_maps_dump_provider.cc

 // 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.
 
 #include "base/trace_event/process_memory_maps_dump_provider.h"
 
-#include "base/files/scoped_file.h"
 #include "base/format_macros.h"
 #include "base/logging.h"
 #include "base/strings/string_util.h"
 #include "base/trace_event/process_memory_dump.h"
 #include "base/trace_event/process_memory_maps.h"
 
 namespace base {
 namespace trace_event {
 
 // static
@@ skipping 116 matching lines @@
 }
 
 }  // namespace
 
 // static
 ProcessMemoryMapsDumpProvider* ProcessMemoryMapsDumpProvider::GetInstance() {
   return Singleton<ProcessMemoryMapsDumpProvider,
                    LeakySingletonTraits<ProcessMemoryMapsDumpProvider>>::get();
 }
 
-ProcessMemoryMapsDumpProvider::ProcessMemoryMapsDumpProvider() {
-}
+ProcessMemoryMapsDumpProvider::ProcessMemoryMapsDumpProvider() {}
 
-ProcessMemoryMapsDumpProvider::~ProcessMemoryMapsDumpProvider() {
-}
+ProcessMemoryMapsDumpProvider::~ProcessMemoryMapsDumpProvider() {}
 
 // Called at trace dump point time. Creates a snapshot of the memory maps for
 // the current process.
 bool ProcessMemoryMapsDumpProvider::OnMemoryDump(const MemoryDumpArgs& args,
                                                  ProcessMemoryDump* pmd) {
   // Snapshot of memory maps is not taken for light dump requests.
   if (args.level_of_detail == MemoryDumpLevelOfDetail::LIGHT)
     return true;
 
   uint32 res = 0;
   if (UNLIKELY(proc_smaps_for_testing)) {
     res = ReadLinuxProcSmapsFile(proc_smaps_for_testing, pmd->process_mmaps());
+  } else if (smaps_file_) {
+    res = ReadLinuxProcSmapsFile(smaps_file_.get(), pmd->process_mmaps());
   } else {
-    ScopedFILE smaps_file(fopen("/proc/self/smaps", "r"));
-    res = ReadLinuxProcSmapsFile(smaps_file.get(), pmd->process_mmaps());
+    ScopedFILE file(fopen("/proc/self/smaps", "r"));
+    res = ReadLinuxProcSmapsFile(file.get(), pmd->process_mmaps());
   }
 
   if (res > 0) {
     pmd->set_has_process_mmaps();
     return true;
   }
   return false;
 }
 
 }  // namespace trace_event
 }  // namespace base