tracing: Add macros for generating context trace events

base/trace_event/common/trace_event_common.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // This header file defines the set of trace_event macros without specifying
 // how the events actually get collected and stored. If you need to expose trace
 // events to some other universe, you can copy-and-paste this file as well as
 // trace_event.h, modifying the macros contained there as necessary for the
 // target platform. The end result is that multiple libraries can funnel events
 // through to a shared trace event collector.
@@ skipping 933 matching lines @@
   INTERNAL_TRACE_EVENT_ADD_WITH_ID_TID_AND_TIMESTAMP(                         \
       TRACE_EVENT_PHASE_SNAPSHOT_OBJECT, category_group, name,                \
       TRACE_ID_DONT_MANGLE(id), TRACE_EVENT_API_CURRENT_THREAD_ID, timestamp, \
       TRACE_EVENT_FLAG_NONE, "snapshot", snapshot)
 
 #define TRACE_EVENT_OBJECT_DELETED_WITH_ID(category_group, name, id) \
   INTERNAL_TRACE_EVENT_ADD_WITH_ID(                                  \
       TRACE_EVENT_PHASE_DELETE_OBJECT, category_group, name,         \
       TRACE_ID_DONT_MANGLE(id), TRACE_EVENT_FLAG_NONE)
 
+// Entering and leaving trace event contexts. |category_group| and |name|
+// specify the context category and type. |context| represents a snapshotted
+// context object.
+#define TRACE_EVENT_ENTER_CONTEXT(category_group, name, context) \
+  INTERNAL_TRACE_EVENT_ADD_WITH_ID(                              \
+      TRACE_EVENT_PHASE_ENTER_CONTEXT, category_group, name,     \
+      TRACE_ID_DONT_MANGLE(context), TRACE_EVENT_FLAG_NONE)
+#define TRACE_EVENT_LEAVE_CONTEXT(category_group, name, context) \
+  INTERNAL_TRACE_EVENT_ADD_WITH_ID(                              \
+      TRACE_EVENT_PHASE_LEAVE_CONTEXT, category_group, name,     \
+      TRACE_ID_DONT_MANGLE(context), TRACE_EVENT_FLAG_NONE)
+#define TRACE_EVENT_SCOPED_CONTEXT(category_group, name, context) \
+  INTERNAL_TRACE_EVENT_SCOPED_CONTEXT(category_group, name, context)
+
 // Macro to efficiently determine if a given category group is enabled.
 #define TRACE_EVENT_CATEGORY_GROUP_ENABLED(category_group, ret)             \
   do {                                                                      \
     INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO(category_group);                 \
     if (INTERNAL_TRACE_EVENT_CATEGORY_GROUP_ENABLED_FOR_RECORDING_MODE()) { \
       *ret = true;                                                          \
     } else {                                                                \
       *ret = false;                                                         \
     }                                                                       \
   } while (0)
@@ skipping 42 matching lines @@
 #define TRACE_EVENT_PHASE_FLOW_STEP ('t')
 #define TRACE_EVENT_PHASE_FLOW_END ('f')
 #define TRACE_EVENT_PHASE_METADATA ('M')
 #define TRACE_EVENT_PHASE_COUNTER ('C')
 #define TRACE_EVENT_PHASE_SAMPLE ('P')
 #define TRACE_EVENT_PHASE_CREATE_OBJECT ('N')
 #define TRACE_EVENT_PHASE_SNAPSHOT_OBJECT ('O')
 #define TRACE_EVENT_PHASE_DELETE_OBJECT ('D')
 #define TRACE_EVENT_PHASE_MEMORY_DUMP ('v')
 #define TRACE_EVENT_PHASE_MARK ('R')
+#define TRACE_EVENT_PHASE_ENTER_CONTEXT ('(')
+#define TRACE_EVENT_PHASE_LEAVE_CONTEXT (')')
 
 // Flags for changing the behavior of TRACE_EVENT_API_ADD_TRACE_EVENT.
 #define TRACE_EVENT_FLAG_NONE (static_cast<unsigned int>(0))
 #define TRACE_EVENT_FLAG_COPY (static_cast<unsigned int>(1 << 0))
 #define TRACE_EVENT_FLAG_HAS_ID (static_cast<unsigned int>(1 << 1))
 #define TRACE_EVENT_FLAG_MANGLE_ID (static_cast<unsigned int>(1 << 2))
 #define TRACE_EVENT_FLAG_SCOPE_OFFSET (static_cast<unsigned int>(1 << 3))
 #define TRACE_EVENT_FLAG_SCOPE_EXTRA (static_cast<unsigned int>(1 << 4))
 #define TRACE_EVENT_FLAG_EXPLICIT_TIMESTAMP (static_cast<unsigned int>(1 << 5))
 #define TRACE_EVENT_FLAG_ASYNC_TTS (static_cast<unsigned int>(1 << 6))
@@ skipping 19 matching lines @@
 
 // Enum reflecting the scope of an INSTANT event. Must fit within
 // TRACE_EVENT_FLAG_SCOPE_MASK.
 #define TRACE_EVENT_SCOPE_GLOBAL (static_cast<unsigned char>(0 << 3))
 #define TRACE_EVENT_SCOPE_PROCESS (static_cast<unsigned char>(1 << 3))
 #define TRACE_EVENT_SCOPE_THREAD (static_cast<unsigned char>(2 << 3))
 
 #define TRACE_EVENT_SCOPE_NAME_GLOBAL ('g')
 #define TRACE_EVENT_SCOPE_NAME_PROCESS ('p')
 #define TRACE_EVENT_SCOPE_NAME_THREAD ('t')