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

components/tracing/tracing_messages.h

Index: components/tracing/tracing_messages.h
diff --git a/components/tracing/tracing_messages.h b/components/tracing/tracing_messages.h
index cd5a2020dda597897478a543e9cba3d1047857de..8322fa962b49946f4cfd541659d07443009ccc5c 100644
--- a/components/tracing/tracing_messages.h
+++ b/components/tracing/tracing_messages.h
@@ -22,14 +22,20 @@
 #define IPC_MESSAGE_START TracingMsgStart
 
 IPC_STRUCT_TRAITS_BEGIN(base::trace_event::TraceLogStatus)
-IPC_STRUCT_TRAITS_MEMBER(event_capacity)
-IPC_STRUCT_TRAITS_MEMBER(event_count)
+  IPC_STRUCT_TRAITS_MEMBER(event_capacity)
+  IPC_STRUCT_TRAITS_MEMBER(event_count)
 IPC_STRUCT_TRAITS_END()
 
+IPC_STRUCT_BEGIN(TracingMsg_MemoryTracingInfo)
+  IPC_STRUCT_MEMBER(uint64, tracing_process_id)
+  IPC_STRUCT_MEMBER(IPC::PlatformFileForTransit, smaps_fd)
+  IPC_STRUCT_MEMBER(IPC::PlatformFileForTransit, status_fd)
+IPC_STRUCT_END()
+
 IPC_STRUCT_TRAITS_BEGIN(base::trace_event::MemoryDumpRequestArgs)
-IPC_STRUCT_TRAITS_MEMBER(dump_guid)
-IPC_STRUCT_TRAITS_MEMBER(dump_type)
-IPC_STRUCT_TRAITS_MEMBER(level_of_detail)
+  IPC_STRUCT_TRAITS_MEMBER(dump_guid)
+  IPC_STRUCT_TRAITS_MEMBER(dump_type)
+  IPC_STRUCT_TRAITS_MEMBER(level_of_detail)
 IPC_STRUCT_TRAITS_END()
 
 IPC_STRUCT_TRAITS_BEGIN(base::trace_event::MemoryDumpArgs)
@@ -44,10 +50,11 @@ IPC_ENUM_TRAITS_MAX_VALUE(
     static_cast<int>(base::trace_event::MemoryDumpType::LAST))
 
 // Sent to all child processes to enable trace event recording.
-IPC_MESSAGE_CONTROL3(TracingMsg_BeginTracing,
-                     std::string /*  trace_config_str */,
-                     base::TraceTicks /* browser_time */,
-                     uint64 /* Tracing process id (hash of child id) */)
+IPC_MESSAGE_CONTROL3(
+    TracingMsg_BeginTracing,
+    std::string /*  trace_config_str */,
+    base::TraceTicks /* browser_time */,
+    TracingMsg_MemoryTracingInfo /* child process' memory tracing info */)
 
 // Sent to all child processes to disable trace event recording.
 IPC_MESSAGE_CONTROL0(TracingMsg_EndTracing)