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 07018b93e0799c1e9134d694ae170961f5303919..49a44b246d8d651f1bd44456f093b5d0905d0f0e 100644
--- a/base/trace_event/trace_event.h
+++ b/base/trace_event/trace_event.h
@@ -555,6 +555,19 @@
       TRACE_EVENT_PHASE_SAMPLE, category_group, name, 0, thread_id, timestamp, \
       TRACE_EVENT_FLAG_NONE, arg1_name, arg1_val, arg2_name, arg2_val)
 
+// TRACE_EVENT_METADATA* events are injected by the sampling profiler.

[dsinclair, 2015/07/02 14:17:05]

nit: remove the bit about being injected by the profile and say something like.
'events are information related to other injected events, not events in their
own right'.

[alph, 2015/07/02 14:59:55]

Done. Thanks.

+#define TRACE_EVENT_METADATA0(category_group, name)                          \
+  INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_METADATA, category_group, name, \
+                           TRACE_EVENT_FLAG_NONE)
+#define TRACE_EVENT_METADATA1(category_group, name, arg1_name, arg1_val)     \
+  INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_METADATA, category_group, name, \
+                           TRACE_EVENT_FLAG_NONE, arg1_name, arg1_val)
+#define TRACE_EVENT_METADATA2(category_group, name, arg1_name, arg1_val,     \
+                              arg2_name, arg2_val)                           \
+  INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_METADATA, category_group, name, \
+                           TRACE_EVENT_FLAG_NONE, arg1_name, arg1_val,       \
+                           arg2_name, arg2_val)
+
 // ASYNC_STEP_* APIs should be only used by legacy code. New code should
 // consider using NESTABLE_ASYNC_* APIs to describe substeps within an async
 // event.