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

content/browser/tracing/trace_message_filter.cc

Index: content/browser/tracing/trace_message_filter.cc
diff --git a/content/browser/tracing/trace_message_filter.cc b/content/browser/tracing/trace_message_filter.cc
index a26c6542b39d379c2094191fd1e94731b608eab0..6d4c6d1e32b4024ea79da20b97107cfa6c983df2 100644
--- a/content/browser/tracing/trace_message_filter.cc
+++ b/content/browser/tracing/trace_message_filter.cc
@@ -9,6 +9,33 @@
 #include "content/browser/tracing/tracing_controller_impl.h"
 #include "content/common/child_process_host_impl.h"
 
+#if defined(OS_LINUX)
+#include <fcntl.h>
+#endif
+
+namespace {
+
+void OpenFilesForProcess(int pid,
+                         TracingMsg_MemoryTracingInfo& memory_tracing_info) {
+#if defined(OS_LINUX)
+  std::string proc_smaps_name = base::StringPrintf("/proc/%d/smaps", pid);
+  int smaps_fd = HANDLE_EINTR(open(proc_smaps_name.c_str(), O_RDONLY));
+  if (smaps_fd != -1) {
+    memory_tracing_info.smaps_fd = IPC::GetFileHandleForProcess(
+        smaps_fd, base::GetCurrentProcessHandle(), true);
+  }
+
+  std::string proc_status_name = base::StringPrintf("/proc/%d/status", pid);
+  int status_fd = HANDLE_EINTR(open(proc_status_name.c_str(), O_RDONLY));
+  if (status_fd != -1) {
+    memory_tracing_info.status_fd = IPC::GetFileHandleForProcess(
+        status_fd, base::GetCurrentProcessHandle(), true);
+  }
+#endif
+}
+
+}  // namespace
+
 namespace content {
 
 TraceMessageFilter::TraceMessageFilter(int child_process_id)
@@ -69,9 +96,15 @@ bool TraceMessageFilter::OnMessageReceived(const IPC::Message& message) {
 
 void TraceMessageFilter::SendBeginTracing(
       const base::trace_event::TraceConfig& trace_config) {
-  DCHECK_CURRENTLY_ON(BrowserThread::UI);
+  TracingMsg_MemoryTracingInfo memory_tracing_info;
+  if (trace_config.IsDetailedMemoryDumpEnabled()) {
+    if (trace_config.IsDetailedMemoryDumpEnabled()) {
+      OpenFilesForProcess(this->peer_pid(), memory_tracing_info);
+    }
+    memory_tracing_info.tracing_process_id = tracing_process_id_;
+  }
   Send(new TracingMsg_BeginTracing(
-      trace_config.ToString(), base::TraceTicks::Now(), tracing_process_id_));
+      trace_config.ToString(), base::TraceTicks::Now(), memory_tracing_info));
 }
 
 void TraceMessageFilter::SendEndTracing() {