Implement a new flow event API that allows binding flow events and regular events.

cc/surfaces/display.cc

Index: cc/surfaces/display.cc
diff --git a/cc/surfaces/display.cc b/cc/surfaces/display.cc
index 54a76efc3d76175fbb2b244f1ee73be4cd6fbe82..f79600d619c4e0bcb88b6b2f118075dabede0dae 100644
--- a/cc/surfaces/display.cc
+++ b/cc/surfaces/display.cc
@@ -207,6 +207,9 @@ bool Display::DrawAndSwap() {
   if (should_draw && !avoid_swap) {
     swapped_since_resize_ = true;
     for (auto& latency : frame->metadata.latency_info) {
+      TRACE_EVENT_WITH_FLOW0("toplevel", "Display::DrawAndSwap",
+                             TRACE_ID_DONT_MANGLE(latency.trace_id),
+                             TRACE_EVENT_FLAG_FLOW_IN | TRACE_EVENT_FLAG_FLOW_OUT);
       TRACE_EVENT_FLOW_STEP0(
           "input,benchmark",
           "LatencyInfo.Flow",