[tracing] Send unique tracing process id for cross-process memory dumps identification.

components/tracing/child_trace_message_filter.h

Index: components/tracing/child_trace_message_filter.h
diff --git a/components/tracing/child_trace_message_filter.h b/components/tracing/child_trace_message_filter.h
index 494d25dfd5e1341fb132d78a620bb67e82dad895..1643e4172b8554ecd1e6d551ed94bab27c8aef15 100644
--- a/components/tracing/child_trace_message_filter.h
+++ b/components/tracing/child_trace_message_filter.h
@@ -41,7 +41,8 @@ class ChildTraceMessageFilter : public IPC::MessageFilter {
  private:
   // Message handlers.
   void OnBeginTracing(const std::string& trace_config_str,
-                      base::TraceTicks browser_time);
+                      base::TraceTicks browser_time,
+                      int unique_process_id_for_tracing);
   void OnEndTracing();
   void OnEnableMonitoring(const std::string& trace_config_str,
                           base::TraceTicks browser_time);