[tracing] Dump child processes' memory metrics in browser

base/trace_event/process_memory_totals_dump_provider.cc

Index: base/trace_event/process_memory_totals_dump_provider.cc
diff --git a/base/trace_event/process_memory_totals_dump_provider.cc b/base/trace_event/process_memory_totals_dump_provider.cc
index a8617207dcfc35350496ebf7b27c8d758c891679..5f74d1efa00b42e40ebd3bdb4f6e0eb6f30ef4e1 100644
--- a/base/trace_event/process_memory_totals_dump_provider.cc
+++ b/base/trace_event/process_memory_totals_dump_provider.cc
@@ -27,26 +27,24 @@ 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() {
 }
@@ -64,9 +62,8 @@ bool ProcessMemoryTotalsDumpProvider::OnMemoryDump(const MemoryDumpArgs& args,
 #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,