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

base/trace_event/trace_event.h

Index: base/trace_event/trace_event.h
diff --git a/base/trace_event/trace_event.h b/base/trace_event/trace_event.h
index 07018b93e0799c1e9134d694ae170961f5303919..edbbb8abf512b7e4809f0fa76f11738a35300385 100644
--- a/base/trace_event/trace_event.h
+++ b/base/trace_event/trace_event.h
@@ -228,11 +228,19 @@
 #define TRACE_EVENT1(category_group, name, arg1_name, arg1_val) \
     INTERNAL_TRACE_MEMORY(category_group, name) \
     INTERNAL_TRACE_EVENT_ADD_SCOPED(category_group, name, arg1_name, arg1_val)
+#define TRACE_EVENT1_WITH_FLOW(category_group, name, arg1_name, arg1_val) \

[dsinclair, 2015/07/14 13:52:10]

These should be TRACE_EVENT_WITH_FLOW1

We put the numbers at the end of all the macros.

+    INTERNAL_TRACE_MEMORY(category_group, name) \
+    INTERNAL_TRACE_EVENT_ADD_SCOPED_WITH_FLOW(category_group, name, arg1_name, arg1_val)
 #define TRACE_EVENT2( \
     category_group, name, arg1_name, arg1_val, arg2_name, arg2_val) \
   INTERNAL_TRACE_MEMORY(category_group, name) \
   INTERNAL_TRACE_EVENT_ADD_SCOPED( \
       category_group, name, arg1_name, arg1_val, arg2_name, arg2_val)
+#define TRACE_EVENT2_WITH_FLOW( \

[dsinclair, 2015/07/14 13:52:10]

Why no TRACE_EVENT_WITH_FLOW0?

+    category_group, name, arg1_name, arg1_val, arg2_name, arg2_val) \
+  INTERNAL_TRACE_MEMORY(category_group, name) \
+  INTERNAL_TRACE_EVENT_ADD_SCOPED_WITH_FLOW( \
+      category_group, name, arg1_name, arg1_val, arg2_name, arg2_val)
 
 // Records events like TRACE_EVENT2 but uses |memory_tag| for memory tracing.
 // Use this where |name| is too generic to accurately aggregate allocations.
@@ -852,6 +860,9 @@
 #define TRACE_EVENT_FLOW_END0(category_group, name, id) \
     INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_FLOW_END, \
         category_group, name, id, TRACE_EVENT_FLAG_NONE)
+#define APPEND_TRACE_EVENT_FLOW_END0(category_group, name, id) \
+    appendFlowEvent(trace_event_internal::constructFlowEvent(TRACE_EVENT_PHASE_FLOW_END, \
+        category_group, name, id, TRACE_EVENT_FLAG_NONE))
 #define TRACE_EVENT_FLOW_END_BIND_TO_ENCLOSING0(category_group, name, id) \
     INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_FLOW_END, \
         category_group, name, id, TRACE_EVENT_FLAG_BIND_TO_ENCLOSING)
@@ -1076,6 +1087,22 @@ TRACE_EVENT_API_CLASS_EXPORT extern \
           INTERNAL_TRACE_EVENT_UID(category_group_enabled), name, h); \
     }
 
+#define INTERNAL_TRACE_EVENT_ADD_SCOPED_WITH_FLOW(category_group, name, ...) \
+    INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO(category_group); \
+    trace_event_internal::ScopedTracer INTERNAL_TRACE_EVENT_UID(tracer); \
+    base::trace_event::TraceEventHandle h = {0, 0, 0}; \
+    if (INTERNAL_TRACE_EVENT_CATEGORY_GROUP_ENABLED_FOR_RECORDING_MODE()) { \
+      h = trace_event_internal::AddTraceEvent( \
+          TRACE_EVENT_PHASE_COMPLETE, \
+          INTERNAL_TRACE_EVENT_UID(category_group_enabled), name, \
+          trace_event_internal::kNoEventId, TRACE_EVENT_FLAG_NONE, \
+          ##__VA_ARGS__); \
+      INTERNAL_TRACE_EVENT_UID(tracer).Initialize( \
+          INTERNAL_TRACE_EVENT_UID(category_group_enabled), name, h); \
+    } \
+    base::trace_event::TraceEventHandleWrapper INTERNAL_TRACE_EVENT_UID(wrapper) (h); \
+    INTERNAL_TRACE_EVENT_UID(wrapper)
+
 // Implementation detail: internal macro to create static category and add
 // event if the category is enabled.
 #define INTERNAL_TRACE_EVENT_ADD_WITH_ID(phase, category_group, name, id, \
@@ -1093,6 +1120,21 @@ TRACE_EVENT_API_CLASS_EXPORT extern \
       } \
     } while (0)
 
+#define INTERNAL_TRACE_EVENT_ADD_WITH_ID_RETURN(phase, category_group, name, id, \
+                                         flags, ...) \
+    INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO(category_group); \
+    if (INTERNAL_TRACE_EVENT_CATEGORY_GROUP_ENABLED_FOR_RECORDING_MODE()) { \
+      unsigned char trace_event_flags = flags | TRACE_EVENT_FLAG_HAS_ID; \
+      trace_event_internal::TraceID trace_event_trace_id( \
+          id, &trace_event_flags); \
+      return trace_event_internal::AddTraceEvent( \
+          phase, INTERNAL_TRACE_EVENT_UID(category_group_enabled), \
+          name, trace_event_trace_id.data(), trace_event_flags, \
+          ##__VA_ARGS__); \
+    } \
+    base::trace_event::TraceEventHandle h = {0, 0, 0}; \
+    return h;
+
 // Implementation detail: internal macro to create static category and add
 // event if the category is enabled.
 #define INTERNAL_TRACE_EVENT_ADD_WITH_ID_TID_AND_TIMESTAMP(phase, \
@@ -1174,6 +1216,10 @@ TRACE_EVENT_API_CLASS_EXPORT extern \
 #define TRACE_EVENT_SCOPE_NAME_PROCESS ('p')
 #define TRACE_EVENT_SCOPE_NAME_THREAD  ('t')
 
+// Type values for identifying flow event direction.
+#define FLOW_IN (static_cast<unsigned char>(0))
+#define FLOW_OUT (static_cast<unsigned char>(1))

[dsinclair, 2015/07/14 13:52:10]

These should be TRACE_EVENT_FLAG_FLOW_IN/OUT. fmeawad@ has a Cl to extend the
unsigned char to a unsigned int.

[fmeawad, 2015/07/14 17:32:57]

The CL has landed.

+
 namespace trace_event_internal {
 
 // Specify these values when the corresponding argument of AddTraceEvent is not
@@ -1600,6 +1646,15 @@ static inline base::trace_event::TraceEventHandle AddTraceEvent(
                                                arg2_name, arg2_val);
 }
 
+static inline base::trace_event::TraceEventHandle constructFlowEvent(
+    char phase,
+    const char *category_group,
+    const char *name,
+    unsigned long long id,
+    unsigned char flags) {
+  INTERNAL_TRACE_EVENT_ADD_WITH_ID_RETURN(phase, category_group, name, id, flags);
+}
+
 // Used by TRACE_EVENTx macros. Do not use directly.
 class TRACE_EVENT_API_CLASS_EXPORT ScopedTracer {
  public: