[tracing] Dump child processes' memory metrics in browser

base/trace_event/process_memory_totals_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_totals_dump_provider.h"
 
 #include "base/process/process_metrics.h"
 #include "base/trace_event/process_memory_dump.h"
 #include "base/trace_event/process_memory_totals.h"
 
 #if defined(OS_LINUX) || defined(OS_ANDROID)
 #include <fcntl.h>
 
 #include "base/files/file_util.h"
 
 namespace {
 bool kernel_supports_rss_peak_reset = true;
 const char kClearPeakRssCommand[] = "5";
 }
 #endif
 
 namespace base {
 namespace trace_event {
 
 // static
 uint64 ProcessMemoryTotalsDumpProvider::rss_bytes_for_testing = 0;
 
 namespace {
 
-ProcessMetrics* CreateProcessMetricsForCurrentProcess() {
+ProcessMetrics* CreateProcessMetrics(ProcessHandle process) {
 #if !defined(OS_MACOSX) || defined(OS_IOS)
-  return ProcessMetrics::CreateProcessMetrics(GetCurrentProcessHandle());
+  return ProcessMetrics::CreateProcessMetrics(process);
 #else
-  return ProcessMetrics::CreateProcessMetrics(GetCurrentProcessHandle(), NULL);
+  return ProcessMetrics::CreateProcessMetrics(process, NULL);
 #endif
 }
 }  // namespace
 
 // static
-ProcessMemoryTotalsDumpProvider*
-ProcessMemoryTotalsDumpProvider::GetInstance() {
-  return Singleton<
-      ProcessMemoryTotalsDumpProvider,
-      LeakySingletonTraits<ProcessMemoryTotalsDumpProvider>>::get();
+scoped_ptr<ProcessMemoryTotalsDumpProvider>
+ProcessMemoryTotalsDumpProvider::CreateForProcess(ProcessHandle process) {
+  return make_scoped_ptr(new ProcessMemoryTotalsDumpProvider(process));
 }
 
-ProcessMemoryTotalsDumpProvider::ProcessMemoryTotalsDumpProvider()
-    : process_metrics_(CreateProcessMetricsForCurrentProcess()) {
-}
+ProcessMemoryTotalsDumpProvider::ProcessMemoryTotalsDumpProvider(
+    ProcessHandle process)
+    : process_(process), process_metrics_(CreateProcessMetrics(process)) {}
 
 ProcessMemoryTotalsDumpProvider::~ProcessMemoryTotalsDumpProvider() {
 }
 
 // Called at trace dump point time. Creates a snapshot the memory counters for
 // the current process.
 bool ProcessMemoryTotalsDumpProvider::OnMemoryDump(const MemoryDumpArgs& args,
                                                    ProcessMemoryDump* pmd) {
   const uint64 rss_bytes = rss_bytes_for_testing
                                ? rss_bytes_for_testing
                                : process_metrics_->GetWorkingSetSize();
 
   uint64 peak_rss_bytes = 0;
 
 #if !defined(OS_IOS)
   peak_rss_bytes = process_metrics_->GetPeakWorkingSetSize();
 #if defined(OS_LINUX) || defined(OS_ANDROID)
-  if (kernel_supports_rss_peak_reset) {
-    // TODO(ssid): Fix crbug.com/461788 to write to the file from sandboxed
-    // processes.
+  // This file cannot be wriiten from other processes. So, do not try.
+  if (kernel_supports_rss_peak_reset && process_ == GetCurrentProcessHandle()) {
     int clear_refs_fd = open("/proc/self/clear_refs", O_WRONLY);
     if (clear_refs_fd > 0 &&
         WriteFileDescriptor(clear_refs_fd, kClearPeakRssCommand,
                             sizeof(kClearPeakRssCommand))) {
       pmd->process_totals()->set_is_peak_rss_resetable(true);
     } else {
       kernel_supports_rss_peak_reset = false;
     }
     close(clear_refs_fd);
   }
 #endif  // defined(OS_LINUX) || defined(OS_ANDROID)
 #endif  // !defined(OS_IOS)
 
   if (rss_bytes > 0) {
     pmd->process_totals()->set_resident_set_bytes(rss_bytes);
     pmd->process_totals()->set_peak_resident_set_bytes(peak_rss_bytes);
     pmd->set_has_process_totals();
     return true;
   }
 
   return false;
 }
 
 }  // namespace trace_event
 }  // namespace base