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

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..0057335e4b46303520644954d8939574dbcb0dde 100644
--- a/base/trace_event/process_memory_totals_dump_provider.cc
+++ b/base/trace_event/process_memory_totals_dump_provider.cc
@@ -34,6 +34,20 @@ ProcessMetrics* CreateProcessMetricsForCurrentProcess() {
   return ProcessMetrics::CreateProcessMetrics(GetCurrentProcessHandle(), NULL);
 #endif
 }
+
+bool ReadStatusFile(int status_fd, std::string* data) {
+  if (lseek(status_fd, 0, SEEK_SET) < 0)
+    return false;
+  char buffer[4096];
+  buffer[0] = '\0';
+  ReadFromFD(status_fd, buffer, sizeof(buffer));
+  if (strlen(buffer) == 0)
+    return false;
+  data->clear();
+  data->append(buffer);
+  return true;
+}
+
 }  // namespace
 
 // static
@@ -45,40 +59,48 @@ ProcessMemoryTotalsDumpProvider::GetInstance() {
 }
 
 ProcessMemoryTotalsDumpProvider::ProcessMemoryTotalsDumpProvider()
-    : process_metrics_(CreateProcessMetricsForCurrentProcess()) {
-}
+    : process_metrics_(CreateProcessMetricsForCurrentProcess()) {}
 
-ProcessMemoryTotalsDumpProvider::~ProcessMemoryTotalsDumpProvider() {
-}
+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 rss_bytes = 0;
   uint64 peak_rss_bytes = 0;
-
+  std::string status_contents;
+
+  if (UNLIKELY(rss_bytes_for_testing)) {
+    rss_bytes = rss_bytes_for_testing;
+#if defined(OS_LINUX)
+  } else if (proc_status_fd_.is_valid() &&
+             ReadStatusFile(proc_status_fd_.get(), &status_contents)) {
+    int res = ParseProcStatusAndGetField(status_contents, "VmRSS", &rss_bytes);
+    DCHECK(res);
+    res = ParseProcStatusAndGetField(status_contents, "VmHWM", &peak_rss_bytes);
+    DCHECK(res);
+#endif
+  } else {
+    rss_bytes = process_metrics_->GetWorkingSetSize();
 #if !defined(OS_IOS)
-  peak_rss_bytes = process_metrics_->GetPeakWorkingSetSize();
+    peak_rss_bytes = process_metrics_->GetPeakWorkingSetSize();
+#endif
+  }
+
 #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.
     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);
+      close(clear_refs_fd);
     } 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);