Change sampler code events phase from instant to meta.

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 ed49fe4656f9326b232f973e69936ad3f31f4af9..a7bdeb917598145849d04f498922ad14e9082b9c 100644
--- a/base/trace_event/trace_event.h
+++ b/base/trace_event/trace_event.h
@@ -7,7 +7,7 @@
 
 // This header file defines implementation details of how the trace macros in
 // trace_event_common.h collect and store trace events. Anything not
-// implementation-specific should go in trace_macros_common.h instead of here.
+// implementation-specific should go in trace_event_common.h instead of here.
 
 #include <stddef.h>
 #include <stdint.h>
@@ -187,9 +187,14 @@
 // Adds a metadata event to the trace log. The |AppendValueAsTraceFormat| method
 // on the convertable value will be called at flush time.

[fmeawad, 2016/02/16 21:47:37]

After a second thought I think it is better to eliminate the version with no
category.

[alph, 2016/02/16 23:19:28]

ok. done

 // TRACE_EVENT_API_ADD_METADATA_EVENT(
-//   const char* event_name,
-//   const char* arg_name,
-//   scoped_refptr<ConvertableToTraceFormat> arg_value)
+//     const char* event_name,
+//     const char* arg_name,
+//     scoped_refptr<ConvertableToTraceFormat> arg_value)
+// TRACE_EVENT_API_ADD_METADATA_EVENT(
+//     const unsigned char* category_group_enabled,
+//     const char* event_name,
+//     const char* arg_name,
+//     scoped_refptr<ConvertableToTraceFormat> arg_value)
 #define TRACE_EVENT_API_ADD_METADATA_EVENT \
     trace_event_internal::AddMetadataEvent
 
@@ -347,8 +352,20 @@ TRACE_EVENT_API_CLASS_EXPORT extern \
     }                                                                         \
   } while (0)
 
-// Implementation detail: internal macro to enter and leave a context based on
-// the current scope.
+// Implementation detail: internal macro to create static category and add
+// metadata event if the category is enabled.
+#define INTERNAL_TRACE_EVENT_METADATA_ADD(category_group, name, ...)        \
+  do {                                                                      \
+    INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO(category_group);                 \
+    if (INTERNAL_TRACE_EVENT_CATEGORY_GROUP_ENABLED_FOR_RECORDING_MODE()) { \
+      TRACE_EVENT_API_ADD_METADATA_EVENT(                                   \
+          INTERNAL_TRACE_EVENT_UID(category_group_enabled), name,           \
+          ##__VA_ARGS__);                                                   \
+    }                                                                       \
+  } while (0)
+
+// Implementation detail: internal macro to enter and leave a
+// context based on the current scope.
 #define INTERNAL_TRACE_EVENT_SCOPED_CONTEXT(category_group, name, context) \
   struct INTERNAL_TRACE_EVENT_UID(ScopedContext) {                         \
    public:                                                                 \
@@ -853,6 +870,39 @@ static inline void AddMetadataEvent(
       convertable_values, TRACE_EVENT_FLAG_NONE);
 }
 
+static inline void AddMetadataEvent(
+    const unsigned char* category_group_enabled,
+    const char* event_name,
+    const char* arg_name,
+    scoped_refptr<base::trace_event::ConvertableToTraceFormat> arg_value) {
+  const char* arg_names[1] = {arg_name};
+  scoped_refptr<base::trace_event::ConvertableToTraceFormat>
+      convertable_values[1] = {arg_value};
+  unsigned char arg_types[1] = {TRACE_VALUE_TYPE_CONVERTABLE};
+  base::trace_event::TraceLog::GetInstance()->AddMetadataEvent(
+      category_group_enabled, event_name,
+      1,  // num_args
+      arg_names, arg_types,
+      nullptr,  // arg_values
+      convertable_values, TRACE_EVENT_FLAG_NONE);
+}
+
+template <class ARG1_TYPE>
+static void AddMetadataEvent(const unsigned char* category_group_enabled,
+                             const char* event_name,
+                             const char* arg_name,
+                             const ARG1_TYPE& arg_val) {
+  const int num_args = 1;
+  const char* arg_names[1] = {arg_name};
+  unsigned char arg_types[1];
+  unsigned long long arg_values[1];
+  SetTraceValue(arg_val, &arg_types[0], &arg_values[0]);
+
+  base::trace_event::TraceLog::GetInstance()->AddMetadataEvent(
+      category_group_enabled, event_name, num_args, arg_names, arg_types,
+      arg_values, nullptr, TRACE_EVENT_FLAG_NONE);
+}
+
 template <class ARG1_TYPE>
 static void AddMetadataEvent(const char* event_name,
                              const char* arg_name,