Add granular file tracing.

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 e0249f5539a181175127ba4df1cc7fc489328f44..c82522ce8c1e3c930651821f3ca479e006b54885 100644
--- a/base/trace_event/trace_event.h
+++ b/base/trace_event/trace_event.h
@@ -542,7 +542,7 @@
       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
+// consider using NESTABLE_ASYNC* APIs to describe substeps within an async
 // event.
 // Records a single ASYNC_BEGIN event called "name" immediately, with 0, 1 or 2
 // associated arguments. If the category is not enabled, then this
@@ -682,7 +682,7 @@
         static_cast<int>(base::PlatformThread::CurrentId()), \
         timestamp, TRACE_EVENT_FLAG_NONE)
 
-// NESTABLE_ASYNC_* APIs are used to describe an async operation, which can
+// NESTABLE_ASYNC* APIs are used to describe an async operation, which can
 // be nested within a NESTABLE_ASYNC event and/or have inner NESTABLE_ASYNC
 // events.
 // - category and name strings must have application lifetime (statics or
@@ -702,8 +702,12 @@
 // NESTABLE_ASYNC event of that id. Corresponding warning messages for
 // unmatched events will be shown in the analysis view.
 
-// Records a single NESTABLE_ASYNC_BEGIN event called "name" immediately, with 2
-// associated arguments. If the category is not enabled, then this does nothing.
+// Records a single NESTABLE_ASYNC_BEGIN event called "name" immediately, with 0
+// or 2 associated arguments. If the category is not enabled, then this does
+// nothing.
+#define TRACE_EVENT_NESTABLE_ASYNC_BEGIN0(category_group, name, id) \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_NESTABLE_ASYNC_BEGIN, \
+        category_group, name, id, TRACE_EVENT_FLAG_NONE)
 #define TRACE_EVENT_NESTABLE_ASYNC_BEGIN2(category_group, name, id, arg1_name, \
         arg1_val, arg2_name, arg2_val) \
     INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_NESTABLE_ASYNC_BEGIN, \
@@ -711,6 +715,13 @@
         arg2_name, arg2_val)
 // Records a single NESTABLE_ASYNC_END event called "name" immediately, with 2
 // associated arguments. If the category is not enabled, then this does nothing.
+#define TRACE_EVENT_NESTABLE_ASYNC_END0(category_group, name, id) \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_NESTABLE_ASYNC_END, \
+        category_group, name, id, TRACE_EVENT_FLAG_NONE)
+#define TRACE_EVENT_NESTABLE_ASYNC_END1(category_group, name, id, arg1_name, \
+        arg1_val) \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_NESTABLE_ASYNC_END, \
+        category_group, name, id, TRACE_EVENT_FLAG_NONE, arg1_name, arg1_val)
 #define TRACE_EVENT_NESTABLE_ASYNC_END2(category_group, name, id, arg1_name, \
         arg1_val, arg2_name, arg2_val) \
     INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_NESTABLE_ASYNC_END, \
@@ -725,6 +736,28 @@
         category_group, name, id, TRACE_EVENT_FLAG_NONE, arg1_name, arg1_val, \
         arg2_name, arg2_val)
 
+// Call TRACE_EVENT_NESTABLE_ASYNC_BEGIN* to set up a nestable id before calling
+// TRACE_EVENT_NESTABLE_ASYNC*. Records a nested pair of begin and end events
+// called "name" for the current scope and assocated with the id passed to
+// _BEGIN. Handles 0, 1 or 2 associated arguments. If the category is
+// not enabled, then this does nothing.
+// - category and name strings must have application lifetime (statics or
+//   literals). They may not include " chars.
+#define TRACE_EVENT_NESTABLE_ASYNC0(category_group, name, id) \
+    INTERNAL_TRACE_EVENT_ADD_SCOPED_WITH_ID( \
+        TRACE_EVENT_PHASE_NESTABLE_ASYNC_COMPLETE, category_group, name, id, \
+        TRACE_EVENT_FLAG_NONE)
+#define TRACE_EVENT_NESTABLE_ASYNC1( \
+        category_group, name, id, arg1_name, arg1_val) \
+    INTERNAL_TRACE_EVENT_ADD_SCOPED_WITH_ID( \
+        TRACE_EVENT_PHASE_NESTABLE_ASYNC_COMPLETE, category_group, name, id, \
+        TRACE_EVENT_FLAG_NONE, arg1_name, arg1_val)
+#define TRACE_EVENT_NESTABLE_ASYNC2( \
+        category_group, name, id, arg1_name, arg1_val, arg2_name, arg2_val) \
+    INTERNAL_TRACE_EVENT_ADD_SCOPED_WITH_ID( \
+        TRACE_EVENT_PHASE_NESTABLE_ASYNC_COMPLETE, category_group, name, id, \
+        TRACE_EVENT_FLAG_NONE, arg1_name, arg1_val, arg2_name, arg2_val)
+
 // Records a single FLOW_BEGIN event called "name" immediately, with 0, 1 or 2
 // associated arguments. If the category is not enabled, then this
 // does nothing.
@@ -1027,6 +1060,26 @@ TRACE_EVENT_API_CLASS_EXPORT extern \
     } while (0)
 
 // Implementation detail: internal macro to create static category and add
+// event if the category is enabled. Also adds the end event when the scope
+// ends.
+#define INTERNAL_TRACE_EVENT_ADD_SCOPED_WITH_ID( \
+        phase, category_group, name, id, flags, ...) \
+    INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO(category_group); \
+    trace_event_internal::ScopedTracer INTERNAL_TRACE_EVENT_UID(tracer); \
+    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); \
+      base::trace_event::TraceEventHandle h = \
+          trace_event_internal::AddTraceEvent( \
+              phase, INTERNAL_TRACE_EVENT_UID(category_group_enabled), \
+              name, trace_event_trace_id.data(), trace_event_flags, \
+              ##__VA_ARGS__); \
+      INTERNAL_TRACE_EVENT_UID(tracer).Initialize( \
+          INTERNAL_TRACE_EVENT_UID(category_group_enabled), name, 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, \
         category_group, name, id, thread_id, timestamp, flags, ...) \
@@ -1061,6 +1114,7 @@ TRACE_EVENT_API_CLASS_EXPORT extern \
 #define TRACE_EVENT_PHASE_ASYNC_END   ('F')
 #define TRACE_EVENT_PHASE_NESTABLE_ASYNC_BEGIN ('b')
 #define TRACE_EVENT_PHASE_NESTABLE_ASYNC_END ('e')
+#define TRACE_EVENT_PHASE_NESTABLE_ASYNC_COMPLETE ('x')
 #define TRACE_EVENT_PHASE_NESTABLE_ASYNC_INSTANT ('n')
 #define TRACE_EVENT_PHASE_FLOW_BEGIN ('s')
 #define TRACE_EVENT_PHASE_FLOW_STEP  ('t')
@@ -1521,10 +1575,10 @@ static inline base::trace_event::TraceEventHandle AddTraceEvent(
 class TRACE_EVENT_API_CLASS_EXPORT ScopedTracer {
  public:
   // Note: members of data_ intentionally left uninitialized. See Initialize.
-  ScopedTracer() : p_data_(NULL) {}
+  ScopedTracer() : initialized_(false) {}

[Dan Beam, 2015/04/30 04:40:13]

forgot i did this. can revert if you want...

 
   ~ScopedTracer() {
-    if (p_data_ && *data_.category_group_enabled)
+    if (initialized_ && *data_.category_group_enabled)
       TRACE_EVENT_API_UPDATE_TRACE_EVENT_DURATION(
           data_.category_group_enabled, data_.name, data_.event_handle);
   }
@@ -1535,7 +1589,7 @@ class TRACE_EVENT_API_CLASS_EXPORT ScopedTracer {
     data_.category_group_enabled = category_group_enabled;
     data_.name = name;
     data_.event_handle = event_handle;
-    p_data_ = &data_;
+    initialized_ = true;
   }
 
  private:
@@ -1549,7 +1603,7 @@ class TRACE_EVENT_API_CLASS_EXPORT ScopedTracer {
     const char* name;
     base::trace_event::TraceEventHandle event_handle;
   };
-  Data* p_data_;
+  bool initialized_;
   Data data_;
 };