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

base/trace_event/trace_event_unittest.cc

Index: base/trace_event/trace_event_unittest.cc
diff --git a/base/trace_event/trace_event_unittest.cc b/base/trace_event/trace_event_unittest.cc
index afee8a90df9572751e7048a6cf1376a747f38574..7690ac8260698e73302347300d31533fa289b5e2 100644
--- a/base/trace_event/trace_event_unittest.cc
+++ b/base/trace_event/trace_event_unittest.cc
@@ -1424,11 +1424,13 @@ TEST_F(TraceEventTestFixture, StaticStringVsString) {
     TraceEventHandle handle1 =
         trace_event_internal::AddTraceEvent(
             TRACE_EVENT_PHASE_INSTANT, category_group_enabled, "name1", 0, 0,
+            trace_event_internal::kNoId,
             "arg1", std::string("argval"), "arg2", std::string("argval"));
     // Test that static TRACE_STR_COPY string arguments are copied.
     TraceEventHandle handle2 =
         trace_event_internal::AddTraceEvent(
             TRACE_EVENT_PHASE_INSTANT, category_group_enabled, "name2", 0, 0,
+            trace_event_internal::kNoId,
             "arg1", TRACE_STR_COPY("argval"),
             "arg2", TRACE_STR_COPY("argval"));
     EXPECT_GT(tracer->GetStatus().event_count, 1u);
@@ -1451,13 +1453,14 @@ TEST_F(TraceEventTestFixture, StaticStringVsString) {
     TraceEventHandle handle1 =
         trace_event_internal::AddTraceEvent(
             TRACE_EVENT_PHASE_INSTANT, category_group_enabled, "name1", 0, 0,
-            "arg1", "argval", "arg2", "argval");
+            trace_event_internal::kNoId, "arg1", "argval", "arg2", "argval");
     // Test that static TRACE_STR_COPY NULL string arguments are not copied.
     const char* str1 = NULL;
     const char* str2 = NULL;
     TraceEventHandle handle2 =
         trace_event_internal::AddTraceEvent(
             TRACE_EVENT_PHASE_INSTANT, category_group_enabled, "name2", 0, 0,
+            trace_event_internal::kNoId,
             "arg1", TRACE_STR_COPY(str1),
             "arg2", TRACE_STR_COPY(str2));
     EXPECT_GT(tracer->GetStatus().event_count, 1u);