Allow tracing in third_party libraries

base/debug/trace_event.h

 // Copyright (c) 2011 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.
 
 // Trace events are for tracking application performance and resource usage.
 // Macros are provided to track:
 //    Begin and end of function calls
 //    Counters
 //
 // Events are issued against categories. Whereas LOG's
@@ skipping 108 matching lines @@
 // A thread safe singleton and mutex are used for thread safety. Category
 // enabled flags are used to limit the performance impact when the system
 // is not enabled.
 //
 // TRACE_EVENT macros first cache a pointer to a category. The categories are
 // statically allocated and safe at all times, even after exit. Fetching a
 // category is protected by the TraceLog::lock_. Multiple threads initializing
 // the static variable is safe, as they will be serialized by the lock and
 // multiple calls will return the same pointer to the category.
 //
-// Then the category.enabled flag is checked. This is a volatile bool, and
+// Then the category_enabled flag is checked. This is a unsigned char, and
 // not intended to be multithread safe. It optimizes access to AddTraceEvent
 // which is threadsafe internally via TraceLog::lock_. The enabled flag may
 // cause some threads to incorrectly call or skip calling AddTraceEvent near
 // the time of the system being enabled or disabled. This is acceptable as
 // we tolerate some data loss while the system is being enabled/disabled and
 // because AddTraceEvent is threadsafe internally and checks the enabled state
 // again under lock.
 //
 // Without the use of these static category pointers and enabled flags all
 // trace points would carry a significant performance cost of aquiring a lock
@@ skipping 13 matching lines @@
 #include <vector>
 
 #include "base/callback.h"
 #include "base/hash_tables.h"
 #include "base/memory/ref_counted_memory.h"
 #include "base/string_util.h"
 #include "base/synchronization/lock.h"
 #include "base/third_party/dynamic_annotations/dynamic_annotations.h"
 #include "base/timer.h"
 
+////////////////////////////////////////////////////////////////////////////////
+// TODO(jbates): split this into a separate header.
+// This header is designed to be give you trace_event macros without specifying
+// how the events actually get collected and stored. If you need to expose trace
+// event to some other universe, you can copy-and-paste this file and just
+// implement these API macros.
+
+// unsigned char*
+//     TRACE_EVENT_API_GET_CATEGORY_ENABLED(const char* category_name)
+#define TRACE_EVENT_API_GET_CATEGORY_ENABLED \
+    base::debug::TraceLog::GetCategoryEnabled
+
+// Returns the threshold_begin_id used by TRACE_IF_LONGER_THAN macros.
+// int TRACE_EVENT_API_ADD_TRACE_EVENT(
+//                    char phase,
+//                    const unsigned char* category_enabled,

[jar (doing other things), 2012/01/12 21:48:43]

nit: IMO, bool is a better type. It adds to readability. I don't believe you
need to fear how it is evaluated if it is garbage.

[jbates, 2012/01/12 22:22:11]

The main reasoning for not using bool in this API is that it allows the tracing
API to be exported to C code. I don't think we have any C libraries where we
need tracing, but it seems a small enough price to pay for compatibility?

+//                    const char* name,
+//                    unsigned long long id,
+//                    int num_args,
+//                    const char** arg_names,
+//                    const unsigned char* arg_types,
+//                    const unsigned long long* arg_values,
+//                    int threshold_begin_id,
+//                    long long threshold,
+//                    unsigned char flags)
+#define TRACE_EVENT_API_ADD_TRACE_EVENT \
+    base::debug::TraceLog::GetInstance()->AddTraceEvent
+
+// void TRACE_EVENT_API_ADD_COUNTER_EVENT(
+//                    const unsigned char* category_enabled,
+//                    const char* name,
+//                    unsigned long long id,
+//                    const char* arg1_name, int arg1_val,
+//                    const char* arg2_name, int arg2_val,
+//                    unsigned char flags)
+#define TRACE_EVENT_API_ADD_COUNTER_EVENT \
+    base::debug::TraceLog::GetInstance()->AddCounterEvent
+
+// Mangle |pointer| with a process ID hash so that if |pointer| occurs on more
+// than one process, it will not collide in the trace data.
+// unsigned long long TRACE_EVENT_API_GET_ID_FROM_POINTER(void* pointer)
+#define TRACE_EVENT_API_GET_ID_FROM_POINTER \
+    base::debug::TraceLog::GetInstance()->GetInterProcessID
+
+////////////////////////////////////////////////////////////////////////////////
+
 // By default, const char* argument values are assumed to have long-lived scope
 // and will not be copied. Use this macro to force a const char* to be copied.
-#define TRACE_STR_COPY(str) base::debug::TraceValue::StringWithCopy(str)
+#define TRACE_STR_COPY(str) \
+    trace_event_internal::TraceStringWithCopy(str)
 
 // Older style trace macros with explicit id and extra data
 // Only these macros result in publishing data to ETW as currently implemented.
 #define TRACE_EVENT_BEGIN_ETW(name, id, extra) \
     base::debug::TraceLog::AddTraceEventEtw( \
         TRACE_EVENT_PHASE_BEGIN, \
         name, reinterpret_cast<const void*>(id), extra)
 
 #define TRACE_EVENT_END_ETW(name, id, extra) \
     base::debug::TraceLog::AddTraceEventEtw( \
         TRACE_EVENT_PHASE_END, \
         name, reinterpret_cast<const void*>(id), extra)
 
 #define TRACE_EVENT_INSTANT_ETW(name, id, extra) \
     base::debug::TraceLog::AddTraceEventEtw( \
         TRACE_EVENT_PHASE_INSTANT, \
         name, reinterpret_cast<const void*>(id), extra)
 
 // Records a pair of begin and end events called "name" for the current
 // scope, with 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_EVENT0(category, name) \
-    TRACE_EVENT1(category, name, NULL, 0)
+    INTERNAL_TRACE_EVENT_ADD_SCOPED(category, name)
 #define TRACE_EVENT1(category, name, arg1_name, arg1_val) \
-    TRACE_EVENT2(category, name, arg1_name, arg1_val, NULL, 0)
+    INTERNAL_TRACE_EVENT_ADD_SCOPED(category, name, arg1_name, arg1_val)
 #define TRACE_EVENT2(category, name, arg1_name, arg1_val, arg2_name, arg2_val) \
-    INTERNAL_TRACE_EVENT_ADD_SCOPED( \
-        category, name, arg1_name, arg1_val, arg2_name, arg2_val)
+    INTERNAL_TRACE_EVENT_ADD_SCOPED(category, name, arg1_name, arg1_val, \
+        arg2_name, arg2_val)
 
 // Same as TRACE_EVENT except that they are not included in official builds.
 #ifdef OFFICIAL_BUILD
 #define UNSHIPPED_TRACE_EVENT0(category, name) (void)0
 #define UNSHIPPED_TRACE_EVENT1(category, name, arg1_name, arg1_val) (void)0
 #define UNSHIPPED_TRACE_EVENT2(category, name, arg1_name, arg1_val, \
                                arg2_name, arg2_val) (void)0
 #define UNSHIPPED_TRACE_EVENT_INSTANT0(category, name) (void)0
 #define UNSHIPPED_TRACE_EVENT_INSTANT1(category, name, arg1_name, arg1_val) \
     (void)0
@@ skipping 16 matching lines @@
     TRACE_EVENT_INSTANT2(category, name, arg1_name, arg1_val, \
                          arg2_name, arg2_val)
 #endif
 
 // Records a single event called "name" immediately, with 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_INSTANT0(category, name) \
-    TRACE_EVENT_INSTANT1(category, name, NULL, 0)
+    INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_INSTANT, \
+        category, name, TRACE_EVENT_FLAG_NONE)
 #define TRACE_EVENT_INSTANT1(category, name, arg1_name, arg1_val) \
-    TRACE_EVENT_INSTANT2(category, name, arg1_name, arg1_val, NULL, 0)
+    INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_INSTANT, \
+        category, name, TRACE_EVENT_FLAG_NONE, arg1_name, arg1_val)
 #define TRACE_EVENT_INSTANT2(category, name, arg1_name, arg1_val, \
         arg2_name, arg2_val) \
     INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_INSTANT, \
-        category, name, arg1_name, arg1_val, arg2_name, arg2_val, \
-        TRACE_EVENT_FLAG_NONE)
+        category, name, TRACE_EVENT_FLAG_NONE, arg1_name, arg1_val, \
+        arg2_name, arg2_val)
 #define TRACE_EVENT_COPY_INSTANT0(category, name) \
-    TRACE_EVENT_COPY_INSTANT1(category, name, NULL, 0)
+    INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_INSTANT, \
+        category, name, TRACE_EVENT_FLAG_COPY)
 #define TRACE_EVENT_COPY_INSTANT1(category, name, arg1_name, arg1_val) \
-    TRACE_EVENT_COPY_INSTANT2(category, name, arg1_name, arg1_val, NULL, 0)
+    INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_INSTANT, \
+        category, name, TRACE_EVENT_FLAG_COPY, arg1_name, arg1_val)
 #define TRACE_EVENT_COPY_INSTANT2(category, name, arg1_name, arg1_val, \
         arg2_name, arg2_val) \
     INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_INSTANT, \
-        category, name, \
-        arg1_name, base::debug::TraceValue::ForceCopy(arg1_val), \
-        arg2_name, base::debug::TraceValue::ForceCopy(arg2_val), \
-        TRACE_EVENT_FLAG_COPY)
+        category, name, TRACE_EVENT_FLAG_COPY, arg1_name, arg1_val, \
+        arg2_name, arg2_val)
 
 // Records a single BEGIN event called "name" immediately, with 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_BEGIN0(category, name) \
-    TRACE_EVENT_BEGIN1(category, name, NULL, 0)
+    INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_BEGIN, \
+        category, name, TRACE_EVENT_FLAG_NONE)
 #define TRACE_EVENT_BEGIN1(category, name, arg1_name, arg1_val) \
-    TRACE_EVENT_BEGIN2(category, name, arg1_name, arg1_val, NULL, 0)
+    INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_BEGIN, \
+        category, name, TRACE_EVENT_FLAG_NONE, arg1_name, arg1_val)
 #define TRACE_EVENT_BEGIN2(category, name, arg1_name, arg1_val, \
         arg2_name, arg2_val) \
     INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_BEGIN, \
-        category, name, arg1_name, arg1_val, arg2_name, arg2_val, \
-        TRACE_EVENT_FLAG_NONE)
+        category, name, TRACE_EVENT_FLAG_NONE, arg1_name, arg1_val, \
+        arg2_name, arg2_val)
 #define TRACE_EVENT_COPY_BEGIN0(category, name) \
-    TRACE_EVENT_COPY_BEGIN1(category, name, NULL, 0)
+    INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_BEGIN, \
+        category, name, TRACE_EVENT_FLAG_COPY)
 #define TRACE_EVENT_COPY_BEGIN1(category, name, arg1_name, arg1_val) \
-    TRACE_EVENT_COPY_BEGIN2(category, name, arg1_name, arg1_val, NULL, 0)
+    INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_BEGIN, \
+        category, name, TRACE_EVENT_FLAG_COPY, arg1_name, arg1_val)
 #define TRACE_EVENT_COPY_BEGIN2(category, name, arg1_name, arg1_val, \
         arg2_name, arg2_val) \
     INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_BEGIN, \
-        category, name, \
-        arg1_name, base::debug::TraceValue::ForceCopy(arg1_val), \
-        arg2_name, base::debug::TraceValue::ForceCopy(arg2_val), \
-        TRACE_EVENT_FLAG_COPY)
+        category, name, TRACE_EVENT_FLAG_COPY, arg1_name, arg1_val, \
+        arg2_name, arg2_val)
 
 // Records a single END event for "name" immediately. 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_END0(category, name) \
-    TRACE_EVENT_END1(category, name, NULL, 0)
+    INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_END, \
+        category, name, TRACE_EVENT_FLAG_NONE)
 #define TRACE_EVENT_END1(category, name, arg1_name, arg1_val) \
-    TRACE_EVENT_END2(category, name, arg1_name, arg1_val, NULL, 0)
+    INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_END, \
+        category, name, TRACE_EVENT_FLAG_NONE, arg1_name, arg1_val)
 #define TRACE_EVENT_END2(category, name, arg1_name, arg1_val, \
         arg2_name, arg2_val) \
     INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_END, \
-        category, name, arg1_name, arg1_val, arg2_name, arg2_val, \
-        TRACE_EVENT_FLAG_NONE)
+        category, name, TRACE_EVENT_FLAG_NONE, arg1_name, arg1_val, \
+        arg2_name, arg2_val)
 #define TRACE_EVENT_COPY_END0(category, name) \
-    TRACE_EVENT_COPY_END1(category, name, NULL, 0)
+    INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_END, \
+        category, name, TRACE_EVENT_FLAG_COPY)
 #define TRACE_EVENT_COPY_END1(category, name, arg1_name, arg1_val) \
-    TRACE_EVENT_COPY_END2(category, name, arg1_name, arg1_val, NULL, 0)
+    INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_END, \
+        category, name, TRACE_EVENT_FLAG_COPY, arg1_name, arg1_val)
 #define TRACE_EVENT_COPY_END2(category, name, arg1_name, arg1_val, \
         arg2_name, arg2_val) \
     INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_END, \
-        category, name, \
-        arg1_name, base::debug::TraceValue::ForceCopy(arg1_val), \
-        arg2_name, base::debug::TraceValue::ForceCopy(arg2_val), \
-        TRACE_EVENT_FLAG_COPY)
+        category, name, TRACE_EVENT_FLAG_COPY, arg1_name, arg1_val, \
+        arg2_name, arg2_val)
 
 // Time threshold event:
 // Only record the event if the duration is greater than the specified
 // threshold_us (time in microseconds).
 // Records a pair of begin and end events called "name" for the current
 // scope, with 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_IF_LONGER_THAN0(threshold_us, category, name) \
-    TRACE_EVENT_IF_LONGER_THAN1(threshold_us, category, name, NULL, 0)
+    INTERNAL_TRACE_EVENT_ADD_SCOPED_IF_LONGER_THAN(threshold_us, category, name)
 #define TRACE_EVENT_IF_LONGER_THAN1( \
-        threshold_us, category, name, arg1_name, arg1_val) \
-    TRACE_EVENT_IF_LONGER_THAN2(threshold_us, category, name, \
-                           arg1_name, arg1_val, NULL, 0)
+    threshold_us, category, name, arg1_name, arg1_val) \
+    INTERNAL_TRACE_EVENT_ADD_SCOPED_IF_LONGER_THAN( \
+        threshold_us, category, name, arg1_name, arg1_val)
 #define TRACE_EVENT_IF_LONGER_THAN2( \
     threshold_us, category, name, arg1_name, arg1_val, arg2_name, arg2_val) \
-    INTERNAL_TRACE_EVENT_ADD_SCOPED_IF_LONGER_THAN(threshold_us, \
-        category, name, arg1_name, arg1_val, arg2_name, arg2_val)
+    INTERNAL_TRACE_EVENT_ADD_SCOPED_IF_LONGER_THAN( \
+        threshold_us, category, name, arg1_name, arg1_val, arg2_name, arg2_val)
 
 // Records the value of a counter called "name" immediately. Value
 // must be representable as a 32 bit integer.
 // - category and name strings must have application lifetime (statics or
 //   literals). They may not include " chars.
 #define TRACE_COUNTER1(category, name, value) \
     TRACE_COUNTER2(category, name, "value", value, NULL, 0)
 #define TRACE_COPY_COUNTER1(category, name, value) \
     TRACE_COPY_COUNTER2(category, name, "value", value, NULL, 0)
 
 // Records the values of a multi-parted counter called "name" immediately.
 // The UI will treat value1 and value2 as parts of a whole, displaying their
 // values as a stacked-bar chart.
 // - category and name strings must have application lifetime (statics or
 //   literals). They may not include " chars.
 #define TRACE_COUNTER2(category, name, value1_name, value1_val, \
         value2_name, value2_val) \
     INTERNAL_TRACE_EVENT_ADD_COUNTER( \
-        category, name, 0, value1_name, value1_val, value2_name, value2_val, \
+        category, name, trace_event_internal::kNoEventId, \
+        value1_name, value1_val, value2_name, value2_val, \
         TRACE_EVENT_FLAG_NONE)
 #define TRACE_COPY_COUNTER2(category, name, value1_name, value1_val, \
         value2_name, value2_val) \
     INTERNAL_TRACE_EVENT_ADD_COUNTER( \
-        category, name, 0, \
-        value1_name, value1_val, \
-        value2_name, value2_val, \
+        category, name, trace_event_internal::kNoEventId, \
+        value1_name, value1_val, value2_name, value2_val, \
         TRACE_EVENT_FLAG_COPY)
 
 // Records the value of a counter called "name" immediately. Value
 // must be representable as a 32 bit integer.
 // - category and name strings must have application lifetime (statics or
 //   literals). They may not include " chars.
 // - |id| is used to disambiguate counters with the same name. It must either
 //   be a pointer or an integer value up to 64 bits. If it's a pointer, the bits
 //   will be xored with a hash of the process ID so that the same pointer on
 //   two different processes will not collide.
@@ skipping 28 matching lines @@
 // Records a single START event called "name" immediately, with 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.
 // - |id| is used to match the START event with the FINISH event. It must either
 //   be a pointer or an integer value up to 64 bits. If it's a pointer, the bits
 //   will be xored with a hash of the process ID so that the same pointer on
 //   two different processes will not collide.
 #define TRACE_EVENT_START0(category, name, id) \
-    TRACE_EVENT_START1(category, name, id, NULL, 0)
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_START, \
+        category, name, id, TRACE_EVENT_FLAG_HAS_ID)
 #define TRACE_EVENT_START1(category, name, id, arg1_name, arg1_val) \
-    TRACE_EVENT_START2(category, name, id, arg1_name, arg1_val, NULL, 0)
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_START, \
+        category, name, id, TRACE_EVENT_FLAG_HAS_ID, arg1_name, arg1_val)
 #define TRACE_EVENT_START2(category, name, id, arg1_name, arg1_val, \
         arg2_name, arg2_val) \
     INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_START, \
-        category, name, id, arg1_name, arg1_val, arg2_name, arg2_val, \
-        TRACE_EVENT_FLAG_HAS_ID)
+        category, name, id, TRACE_EVENT_FLAG_HAS_ID, \
+        arg1_name, arg1_val, arg2_name, arg2_val)
 #define TRACE_EVENT_COPY_START0(category, name, id) \
-    TRACE_EVENT_COPY_START1(category, name, id, NULL, 0)
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_START, \
+        category, name, id, TRACE_EVENT_FLAG_HAS_ID | TRACE_EVENT_FLAG_COPY)
 #define TRACE_EVENT_COPY_START1(category, name, id, arg1_name, arg1_val) \
-    TRACE_EVENT_COPY_START2(category, name, id, arg1_name, arg1_val, NULL, 0)
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_START, \
+        category, name, id, TRACE_EVENT_FLAG_HAS_ID | TRACE_EVENT_FLAG_COPY, \
+        arg1_name, arg1_val)
 #define TRACE_EVENT_COPY_START2(category, name, id, arg1_name, arg1_val, \
         arg2_name, arg2_val) \
     INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_START, \
-        category, name, id, \
-        arg1_name, base::debug::TraceValue::ForceCopy(arg1_val), \
-        arg2_name, base::debug::TraceValue::ForceCopy(arg2_val), \
-        TRACE_EVENT_FLAG_HAS_ID | TRACE_EVENT_FLAG_COPY)
+        category, name, id, TRACE_EVENT_FLAG_HAS_ID | TRACE_EVENT_FLAG_COPY, \
+        arg1_name, arg1_val, arg2_name, arg2_val)
 
 // Records a single FINISH event for "name" immediately. If the category
 // is not enabled, then this does nothing.
 #define TRACE_EVENT_FINISH0(category, name, id) \
-    TRACE_EVENT_FINISH1(category, name, id, NULL, 0)
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_FINISH, \
+        category, name, id, TRACE_EVENT_FLAG_HAS_ID)
 #define TRACE_EVENT_FINISH1(category, name, id, arg1_name, arg1_val) \
-    TRACE_EVENT_FINISH2(category, name, id, arg1_name, arg1_val, NULL, 0)
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_FINISH, \
+        category, name, id, TRACE_EVENT_FLAG_HAS_ID, arg1_name, arg1_val)
 #define TRACE_EVENT_FINISH2(category, name, id, arg1_name, arg1_val, \
         arg2_name, arg2_val) \
     INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_FINISH, \
-        category, name, id, arg1_name, arg1_val, arg2_name, arg2_val, \
-        TRACE_EVENT_FLAG_HAS_ID)
+        category, name, id, TRACE_EVENT_FLAG_HAS_ID, \
+        arg1_name, arg1_val, arg2_name, arg2_val)
 #define TRACE_EVENT_COPY_FINISH0(category, name, id) \
-    TRACE_EVENT_COPY_FINISH1(category, name, id, NULL, 0)
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_FINISH, \
+        category, name, id, TRACE_EVENT_FLAG_HAS_ID | TRACE_EVENT_FLAG_COPY)
 #define TRACE_EVENT_COPY_FINISH1(category, name, id, arg1_name, arg1_val) \
-    TRACE_EVENT_COPY_FINISH2(category, name, id, arg1_name, arg1_val, NULL, 0)
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_FINISH, \
+        category, name, id, TRACE_EVENT_FLAG_HAS_ID | TRACE_EVENT_FLAG_COPY, \
+        arg1_name, arg1_val)
 #define TRACE_EVENT_COPY_FINISH2(category, name, id, arg1_name, arg1_val, \
         arg2_name, arg2_val) \
     INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_FINISH, \
-        category, name, id, \
-        arg1_name, base::debug::TraceValue::ForceCopy(arg1_val), \
-        arg2_name, base::debug::TraceValue::ForceCopy(arg2_val), \
-        TRACE_EVENT_FLAG_HAS_ID | TRACE_EVENT_FLAG_COPY)
+        category, name, id, TRACE_EVENT_FLAG_HAS_ID | TRACE_EVENT_FLAG_COPY, \
+        arg1_name, arg1_val, arg2_name, arg2_val)
 
 
 // Implementation detail: trace event macros create temporary variables
 // to keep instrumentation overhead low. These macros give each temporary
 // variable a unique name based on the line number to prevent name collissions.
 #define INTERNAL_TRACE_EVENT_UID3(a,b) \
     trace_event_unique_##a##b
 #define INTERNAL_TRACE_EVENT_UID2(a,b) \
     INTERNAL_TRACE_EVENT_UID3(a,b)
 #define INTERNAL_TRACE_EVENT_UID(name_prefix) \
     INTERNAL_TRACE_EVENT_UID2(name_prefix, __LINE__)
 
 // Implementation detail: internal macro to create static category.
 // - ANNOTATE_BENIGN_RACE, see Thread Safety above.
 #define INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO(category) \
-    static const base::debug::TraceCategory* \
-        INTERNAL_TRACE_EVENT_UID(catstatic) = NULL; \
+    static const unsigned char* INTERNAL_TRACE_EVENT_UID(catstatic) = NULL; \
     ANNOTATE_BENIGN_RACE(&INTERNAL_TRACE_EVENT_UID(catstatic), \
                          "trace_event category"); \
     if (!INTERNAL_TRACE_EVENT_UID(catstatic)) \
       INTERNAL_TRACE_EVENT_UID(catstatic) = \
-          base::debug::TraceLog::GetCategory(category);
+          TRACE_EVENT_API_GET_CATEGORY_ENABLED(category);
 
 // Implementation detail: internal macro to create static category and add
 // event if the category is enabled.
-#define INTERNAL_TRACE_EVENT_ADD( \
-      phase, category, name, arg1_name, arg1_val, arg2_name, arg2_val, flags) \
+#define INTERNAL_TRACE_EVENT_ADD(phase, category, name, flags, ...) \
     INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO(category); \
-    if (INTERNAL_TRACE_EVENT_UID(catstatic)->enabled) { \
-      base::debug::TraceLog::GetInstance()->AddTraceEvent( \
-          phase, INTERNAL_TRACE_EVENT_UID(catstatic), \
-          name, 0, arg1_name, arg1_val, arg2_name, arg2_val, -1, 0, flags); \
+    if (*INTERNAL_TRACE_EVENT_UID(catstatic)) { \
+      trace_event_internal::AddTraceEvent( \
+          phase, INTERNAL_TRACE_EVENT_UID(catstatic), name, \
+          trace_event_internal::kNoEventId, flags, ##__VA_ARGS__); \
     }
 
 // Implementation detail: internal macro to create static category and
 // add the counter event if it is enabled.
 #define INTERNAL_TRACE_EVENT_ADD_COUNTER( \
       category, name, id, arg1_name, arg1_val, arg2_name, arg2_val, flags) \
     INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO(category); \
-    if (INTERNAL_TRACE_EVENT_UID(catstatic)->enabled) { \
-      base::debug::TraceLog::GetInstance()->AddCounterEvent( \
+    if (*INTERNAL_TRACE_EVENT_UID(catstatic)) { \
+      TRACE_EVENT_API_ADD_COUNTER_EVENT( \
           INTERNAL_TRACE_EVENT_UID(catstatic), \
-          name, id, arg1_name, arg1_val, arg2_name, arg2_val, flags); \
+          name, trace_event_internal::TraceID(id).data(), \
+          arg1_name, arg1_val, arg2_name, arg2_val, flags); \
     }
 
 // Implementation detail: internal macro to create static category and add begin
 // event if the category is enabled. Also adds the end event when the scope
 // ends.
-#define INTERNAL_TRACE_EVENT_ADD_SCOPED( \
-      category, name, arg1_name, arg1_val, arg2_name, arg2_val) \
+#define INTERNAL_TRACE_EVENT_ADD_SCOPED(category, name, ...) \
     INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO(category); \
-    base::debug::internal::TraceEndOnScopeClose \
+    trace_event_internal::TraceEndOnScopeClose \
         INTERNAL_TRACE_EVENT_UID(profileScope); \
-    if (INTERNAL_TRACE_EVENT_UID(catstatic)->enabled) { \
-      base::debug::TraceLog::GetInstance()->AddTraceEvent( \
+    if (*INTERNAL_TRACE_EVENT_UID(catstatic)) { \
+      trace_event_internal::AddTraceEvent( \
           TRACE_EVENT_PHASE_BEGIN, \
           INTERNAL_TRACE_EVENT_UID(catstatic), \
-          name, 0, arg1_name, arg1_val, arg2_name, arg2_val, -1, 0, \
-          TRACE_EVENT_FLAG_NONE); \
+          name, trace_event_internal::kNoEventId, \
+          TRACE_EVENT_FLAG_NONE, ##__VA_ARGS__); \
       INTERNAL_TRACE_EVENT_UID(profileScope).Initialize( \
           INTERNAL_TRACE_EVENT_UID(catstatic), name); \
     }
 
 // Implementation detail: internal macro to create static category and add begin
 // event if the category is enabled. Also adds the end event when the scope
 // ends. If the elapsed time is < threshold time, the begin/end pair is erased.
 #define INTERNAL_TRACE_EVENT_ADD_SCOPED_IF_LONGER_THAN(threshold, \
-      category, name, arg1_name, arg1_val, arg2_name, arg2_val) \
+        category, name, ...) \
     INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO(category); \
-    base::debug::internal::TraceEndOnScopeCloseThreshold \
+    trace_event_internal::TraceEndOnScopeCloseThreshold \
         INTERNAL_TRACE_EVENT_UID(profileScope); \
-    if (INTERNAL_TRACE_EVENT_UID(catstatic)->enabled) { \
+    if (*INTERNAL_TRACE_EVENT_UID(catstatic)) { \
       int INTERNAL_TRACE_EVENT_UID(begin_event_id) = \
-        base::debug::TraceLog::GetInstance()->AddTraceEvent( \
+        trace_event_internal::AddTraceEvent( \
             TRACE_EVENT_PHASE_BEGIN, \
             INTERNAL_TRACE_EVENT_UID(catstatic), \
-            name, 0, arg1_name, arg1_val, arg2_name, arg2_val, -1, 0, \
-            TRACE_EVENT_FLAG_NONE); \
+            name, trace_event_internal::kNoEventId, \
+            TRACE_EVENT_FLAG_NONE, ##__VA_ARGS__); \
       INTERNAL_TRACE_EVENT_UID(profileScope).Initialize( \
           INTERNAL_TRACE_EVENT_UID(catstatic), name, \
           INTERNAL_TRACE_EVENT_UID(begin_event_id), threshold); \
     }
 
 // 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, name, id, \
-      arg1_name, arg1_val, arg2_name, arg2_val, flags) \
+#define INTERNAL_TRACE_EVENT_ADD_WITH_ID(phase, category, name, id, flags, \
+                                         ...) \
     INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO(category); \
-    if (INTERNAL_TRACE_EVENT_UID(catstatic)->enabled) { \
-      base::debug::TraceLog::GetInstance()->AddTraceEvent( \
+    if (*INTERNAL_TRACE_EVENT_UID(catstatic)) { \
+      trace_event_internal::AddTraceEvent( \
           phase, INTERNAL_TRACE_EVENT_UID(catstatic), \
-          name, id, arg1_name, arg1_val, arg2_name, arg2_val, -1, 0, flags); \
+          name, trace_event_internal::TraceID(id).data(), flags, \
+          ##__VA_ARGS__); \
     }
 
 template <typename Type>
 struct StaticMemorySingletonTraits;
 
 namespace base {
 
 class RefCountedString;
 
 namespace debug {
 
-// Categories allow enabling/disabling of streams of trace events
-struct TraceCategory {
-  const char* name;
-  volatile bool enabled;
-};
+const int kTraceMaxNumArgs = 2;
 
-const size_t kTraceMaxNumArgs = 2;
+// Notes regarding the following definitions:
+// New values can be added and propagated to third party libraries, but existing
+// definitions must never be changed, because third party libraries may use old
+// definitions.
 
 // Phase indicates the nature of an event entry. E.g. part of a begin/end pair.
-typedef char TraceEventPhase;
-#define TRACE_EVENT_PHASE_BEGIN     (base::debug::TraceEventPhase('B'))
-#define TRACE_EVENT_PHASE_END       (base::debug::TraceEventPhase('E'))
-#define TRACE_EVENT_PHASE_INSTANT   (base::debug::TraceEventPhase('I'))
-#define TRACE_EVENT_PHASE_START     (base::debug::TraceEventPhase('S'))
-#define TRACE_EVENT_PHASE_FINISH    (base::debug::TraceEventPhase('F'))
-#define TRACE_EVENT_PHASE_METADATA  (base::debug::TraceEventPhase('M'))
-#define TRACE_EVENT_PHASE_COUNTER   (base::debug::TraceEventPhase('C'))
+#define TRACE_EVENT_PHASE_BEGIN    ('B')
+#define TRACE_EVENT_PHASE_END      ('E')
+#define TRACE_EVENT_PHASE_INSTANT  ('I')
+#define TRACE_EVENT_PHASE_START    ('S')
+#define TRACE_EVENT_PHASE_FINISH   ('F')
+#define TRACE_EVENT_PHASE_METADATA ('M')
+#define TRACE_EVENT_PHASE_COUNTER  ('C')
 
-typedef uint8 TraceEventFlags;
-#define TRACE_EVENT_FLAG_NONE        (base::debug::TraceEventFlags(0))
-#define TRACE_EVENT_FLAG_COPY        (base::debug::TraceEventFlags(1<<0))
-#define TRACE_EVENT_FLAG_HAS_ID      (base::debug::TraceEventFlags(1<<1))
+// Flags for changing the behavior of TRACE_EVENT_API_ADD_TRACE_EVENT.
+#define TRACE_EVENT_FLAG_NONE        (static_cast<unsigned char>(0))
+#define TRACE_EVENT_FLAG_COPY        (static_cast<unsigned char>(1<<0))
+#define TRACE_EVENT_FLAG_HAS_ID      (static_cast<unsigned char>(1<<1))
 
-// Simple union of values. This is much lighter weight than base::Value, which
-// requires dynamic allocation and a vtable. To keep the trace runtime overhead
-// low, we want constant size storage here.
-class BASE_EXPORT TraceValue {
- public:
-  enum Type {
-    TRACE_TYPE_UNDEFINED,
-    TRACE_TYPE_BOOL,
-    TRACE_TYPE_UINT,
-    TRACE_TYPE_INT,
-    TRACE_TYPE_DOUBLE,
-    TRACE_TYPE_POINTER,
-    TRACE_TYPE_STRING,
-    TRACE_TYPE_STATIC_STRING
-  };
-
-  TraceValue() : type_(TRACE_TYPE_UNDEFINED) {
-    value_.as_uint = 0ull;
-  }
-  TraceValue(bool rhs) : type_(TRACE_TYPE_BOOL) {
-    value_.as_bool = rhs;
-  }
-  TraceValue(uint64 rhs) : type_(TRACE_TYPE_UINT) {
-    value_.as_uint = rhs;
-  }
-  TraceValue(uint32 rhs) : type_(TRACE_TYPE_UINT) {
-    value_.as_uint = rhs;
-  }
-  TraceValue(uint16 rhs) : type_(TRACE_TYPE_UINT) {
-    value_.as_uint = rhs;
-  }
-  TraceValue(uint8 rhs) : type_(TRACE_TYPE_UINT) {
-    value_.as_uint = rhs;
-  }
-  TraceValue(int64 rhs) : type_(TRACE_TYPE_INT) {
-    value_.as_int = rhs;
-  }
-  TraceValue(int32 rhs) : type_(TRACE_TYPE_INT) {
-    value_.as_int = rhs;
-  }
-  TraceValue(int16 rhs) : type_(TRACE_TYPE_INT) {
-    value_.as_int = rhs;
-  }
-  TraceValue(int8 rhs) : type_(TRACE_TYPE_INT) {
-    value_.as_int = rhs;
-  }
-  TraceValue(double rhs) : type_(TRACE_TYPE_DOUBLE) {
-    value_.as_double = rhs;
-  }
-  TraceValue(const void* rhs) : type_(TRACE_TYPE_POINTER) {
-    value_.as_pointer = rhs;
-  }
-  TraceValue(const std::string& rhs) : type_(TRACE_TYPE_STRING) {
-    value_.as_string = rhs.c_str();
-  }
-  TraceValue(const char* rhs) : type_(TRACE_TYPE_STATIC_STRING) {
-    value_.as_string = rhs;
-  }
-
-  static TraceValue StringWithCopy(const char* rhs) {
-    TraceValue value(rhs);
-    if (rhs)
-      value.type_ = TRACE_TYPE_STRING;
-    return value;
-  }
-
-  static TraceValue ForceCopy(const TraceValue& rhs) {
-    TraceValue value(rhs);
-    if (value.type_ == TRACE_TYPE_STATIC_STRING && value.as_string())
-      value.type_ = TRACE_TYPE_STRING;
-    return value;
-  }
-
-  bool is_string() const {
-    return type_ == TRACE_TYPE_STRING || type_ == TRACE_TYPE_STATIC_STRING;
-  }
-
-  void AppendAsJSON(std::string* out) const;
-
-  Type type() const {
-    return type_;
-  }
-  uint64 as_uint() const {
-    DCHECK_EQ(TRACE_TYPE_UINT, type_);
-    return value_.as_uint;
-  }
-  bool as_bool() const {
-    DCHECK_EQ(TRACE_TYPE_BOOL, type_);
-    return value_.as_bool;
-  }
-  int64 as_int() const {
-    DCHECK_EQ(TRACE_TYPE_INT, type_);
-    return value_.as_int;
-  }
-  double as_double() const {
-    DCHECK_EQ(TRACE_TYPE_DOUBLE, type_);
-    return value_.as_double;
-  }
-  const void* as_pointer() const {
-    DCHECK_EQ(TRACE_TYPE_POINTER, type_);
-    return value_.as_pointer;
-  }
-  const char* as_string() const {
-    DCHECK(is_string());
-    return value_.as_string;
-  }
-  const char** as_assignable_string() {
-    DCHECK_EQ(TRACE_TYPE_STRING, type_);
-    return &value_.as_string;
-  }
-
- private:
-  union Value {
-    bool as_bool;
-    uint64 as_uint;
-    int64 as_int;
-    double as_double;
-    const void* as_pointer;
-    const char* as_string;
-  };
-
-  Type type_;
-  Value value_;
-};
-
-// TraceID encapsulates an ID that can either be an integer or pointer. Pointers
-// are mangled with the Process ID so that they are unlikely to collide when the
-// same pointer is used on different processes.
-class BASE_EXPORT TraceID {
- public:
-  TraceID() : data_(0u) {}
-  TraceID(void* rhs);
-  TraceID(unsigned long long rhs) : data_(static_cast<uint64>(rhs)) {}
-  TraceID(unsigned long rhs) : data_(static_cast<uint64>(rhs)) {}
-  TraceID(unsigned int rhs) : data_(static_cast<uint64>(rhs)) {}
-  TraceID(long long rhs) : data_(static_cast<uint64>(rhs)) {}
-  TraceID(long rhs) : data_(static_cast<uint64>(rhs)) {}
-  TraceID(int rhs) : data_(static_cast<uint64>(rhs)) {}
-
-  uint64 data() const { return data_; }
-
- private:
-  uint64 data_;
-};
+// Type values for identifying types in the TraceValue union.
+#define TRACE_VALUE_TYPE_BOOL         (static_cast<unsigned char>(1))
+#define TRACE_VALUE_TYPE_UINT         (static_cast<unsigned char>(2))
+#define TRACE_VALUE_TYPE_INT          (static_cast<unsigned char>(3))
+#define TRACE_VALUE_TYPE_DOUBLE       (static_cast<unsigned char>(4))
+#define TRACE_VALUE_TYPE_POINTER      (static_cast<unsigned char>(5))
+#define TRACE_VALUE_TYPE_STRING       (static_cast<unsigned char>(6))
+#define TRACE_VALUE_TYPE_COPY_STRING  (static_cast<unsigned char>(7))
 
 // Output records are "Events" and can be obtained via the
 // OutputCallback whenever the tracing system decides to flush. This
 // can happen at any time, on any thread, or you can programatically
 // force it to happen.
 class BASE_EXPORT TraceEvent {
  public:
+  union TraceValue {
+    bool as_bool;
+    unsigned long long as_uint;
+    long long as_int;
+    double as_double;
+    const void* as_pointer;
+    const char* as_string;
+  };
+
   TraceEvent();
   TraceEvent(int thread_id,
              TimeTicks timestamp,
-             TraceEventPhase phase,
-             const TraceCategory* category,
+             char phase,
+             const unsigned char* category_enabled,
              const char* name,
-             TraceID id,
-             const char* arg1_name, const TraceValue& arg1_val,
-             const char* arg2_name, const TraceValue& arg2_val,
-             TraceEventFlags flags);
+             unsigned long long id,
+             int num_args,
+             const char** arg_names,
+             const unsigned char* arg_types,
+             const unsigned long long* arg_values,
+             unsigned char flags);
   ~TraceEvent();
 
-  static char GetPhaseChar(TraceEventPhase phase) {
-    return static_cast<char>(phase);
-  }
-
-  static TraceEventPhase GetPhase(const char* phase) {
-    return static_cast<TraceEventPhase>(*phase);
-  }
-
   // Serialize event data to JSON
   static void AppendEventsAsJSON(const std::vector<TraceEvent>& events,
                                  size_t start,
                                  size_t count,
                                  std::string* out);
   void AppendAsJSON(std::string* out) const;
 
   TimeTicks timestamp() const { return timestamp_; }
 
   // Exposed for unittesting:
 
   const base::RefCountedString* parameter_copy_storage() const {
     return parameter_copy_storage_.get();
   }
 
   const char* name() const { return name_; }
 
  private:
   // Note: these are ordered by size (largest first) for optimal packing.
   TimeTicks timestamp_;
   // id_ can be used to store phase-specific data.
-  TraceID id_;
+  unsigned long long id_;
   TraceValue arg_values_[kTraceMaxNumArgs];
   const char* arg_names_[kTraceMaxNumArgs];
-  const TraceCategory* category_;
+  const unsigned char* category_enabled_;
   const char* name_;
   scoped_refptr<base::RefCountedString> parameter_copy_storage_;
   int thread_id_;
-  TraceEventPhase phase_;
-  TraceEventFlags flags_;
+  char phase_;
+  unsigned char flags_;
+  unsigned char arg_types_[kTraceMaxNumArgs];
 };
 
 
 // TraceResultBuffer collects and converts trace fragments returned by TraceLog
 // to JSON output.
 class BASE_EXPORT TraceResultBuffer {
  public:
   typedef base::Callback<void(const std::string&)> OutputCallback;
 
   // If you don't need to stream JSON chunks out efficiently, and just want to
@@ skipping 89 matching lines @@
   // The trace buffer does not flush dynamically, so when it fills up,
   // subsequent trace events will be dropped. This callback is generated when
   // the trace buffer is full. The callback must be thread safe.
   typedef base::Callback<void(void)> BufferFullCallback;
   void SetBufferFullCallback(const BufferFullCallback& cb);
 
   // Flushes all logged data to the callback.
   void Flush();
 
   // Called by TRACE_EVENT* macros, don't call this directly.
-  static const TraceCategory* GetCategory(const char* name);
+  static const unsigned char* GetCategoryEnabled(const char* name);
+  static const char* GetCategoryName(const unsigned char* category_enabled);
 
   // Called by TRACE_EVENT* macros, don't call this directly.
   // Returns the index in the internal vector of the event if it was added, or
   //         -1 if the event was not added.
   // On end events, the return value of the begin event can be specified along
   // with a threshold in microseconds. If the elapsed time between begin and end
   // is less than the threshold, the begin/end event pair is dropped.
   // If |copy| is set, |name|, |arg_name1| and |arg_name2| will be deep copied
   // into the event; see "Memory scoping note" and TRACE_EVENT_COPY_XXX above.
-  int AddTraceEvent(TraceEventPhase phase,
-                    const TraceCategory* category,
+  int AddTraceEvent(char phase,
+                    const unsigned char* category_enabled,
                     const char* name,
-                    TraceID id,
-                    const char* arg1_name, TraceValue arg1_val,
-                    const char* arg2_name, TraceValue arg2_val,
+                    unsigned long long id,
+                    int num_args,
+                    const char** arg_names,
+                    const unsigned char* arg_types,
+                    const unsigned long long* arg_values,
                     int threshold_begin_id,
-                    int64 threshold,
-                    TraceEventFlags flags);
-  static void AddTraceEventEtw(TraceEventPhase phase,
+                    long long threshold,

[jar (doing other things), 2012/01/12 21:48:43]

nit: Style guide argues for types like int64.  I'm not sure why you changed
these.

I'd suggest sticking with the well defined (sized) types that google3 (or our
base types) define.

[jbates, 2012/01/12 22:22:11]

In order to make this API available to third party libraries, we can't depend on
the int64 type family because it's only valid in chromium. I believe this is
done for other chromium APIs as well where they are called via WebKit, for
example.

+                    unsigned char flags);
+  static void AddTraceEventEtw(char phase,
                                const char* name,
                                const void* id,
                                const char* extra);
-  static void AddTraceEventEtw(TraceEventPhase phase,
+  static void AddTraceEventEtw(char phase,
                                const char* name,
                                const void* id,
                                const std::string& extra);
 
   // A wrapper around AddTraceEvent used by TRACE_COUNTERx macros
   // that allows only integer values for the counters.
-  int AddCounterEvent(const TraceCategory* category,
-                      const char* name,
-                      TraceID id,
-                      const char* arg1_name, int32 arg1_val,
-                      const char* arg2_name, int32 arg2_val,
-                      TraceEventFlags flags);
+  void AddCounterEvent(const unsigned char* category_enabled,
+                       const char* name,
+                       unsigned long long id,
+                       const char* arg1_name, int arg1_val,
+                       const char* arg2_name, int arg2_val,
+                       unsigned char flags);
 
-  // Mangle |id| with a hash based on the process ID so that if |id| occurs on
+  // Mangle |ptr| with a hash based on the process ID so that if |ptr| occurs on
   // more than one process, it will not collide.
-  uint64 GetIntraProcessID(uint64 id) const { return id ^ process_id_hash_; }
+  unsigned long long GetInterProcessID(void* ptr) const {
+    return static_cast<unsigned long long>(reinterpret_cast<uintptr_t>(ptr)) ^
+           process_id_hash_;
+  }
 
   int process_id() const { return process_id_; }
 
   // Exposed for unittesting:
 
   // Allows deleting our singleton instance.
   static void DeleteForTesting();
 
   // Allows resurrecting our singleton instance post-AtExit processing.
   static void Resurrect();
 
   // Allow tests to inspect TraceEvents.
   size_t GetEventsSize() const { return logged_events_.size(); }
   const TraceEvent& GetEventAt(size_t index) const {
     DCHECK(index < logged_events_.size());
     return logged_events_[index];
   }
 
   void SetProcessID(int process_id);
 
  private:
   // This allows constructor and destructor to be private and usable only
   // by the Singleton class.
   friend struct StaticMemorySingletonTraits<TraceLog>;
 
   TraceLog();
   ~TraceLog();
-  const TraceCategory* GetCategoryInternal(const char* name);
+  const unsigned char* GetCategoryEnabledInternal(const char* name);
   void AddThreadNameMetadataEvents();
   void AddClockSyncMetadataEvents();
 
   // TODO(nduca): switch to per-thread trace buffers to reduce thread
   // synchronization.
   Lock lock_;
   bool enabled_;
   OutputCallback output_callback_;
   BufferFullCallback buffer_full_callback_;
   std::vector<TraceEvent> logged_events_;
   std::vector<std::string> included_categories_;
   std::vector<std::string> excluded_categories_;
 
   base::hash_map<int, std::string> thread_names_;
 
   // XORed with TraceID to make it unlikely to collide with other processes.
-  uint64 process_id_hash_;
+  unsigned long long process_id_hash_;
 
   int process_id_;
 
   DISALLOW_COPY_AND_ASSIGN(TraceLog);
 };
 
-namespace internal {
+}  // namespace debug
+}  // namespace base
+
+namespace trace_event_internal {
+
+// Specify these values when the corresponding argument of AddTraceEvent is not
+// used.
+const int kZeroNumArgs = 0;
+const int kNoThreshholdBeginId = -1;
+const long long kNoThresholdValue = 0;
+const unsigned long long kNoEventId = 0;
+
+// TraceID encapsulates an ID that can either be an integer or pointer. Pointers
+// are mangled with the Process ID so that they are unlikely to collide when the
+// same pointer is used on different processes.
+class BASE_EXPORT TraceID {
+ public:
+  explicit TraceID(void* rhs) :
+      data_(TRACE_EVENT_API_GET_ID_FROM_POINTER(rhs)) {}
+  explicit TraceID(unsigned long long rhs) : data_(rhs) {}
+  explicit TraceID(unsigned long rhs) : data_(rhs) {}
+  explicit TraceID(unsigned int rhs) : data_(rhs) {}
+  explicit TraceID(unsigned short rhs) : data_(rhs) {}
+  explicit TraceID(unsigned char rhs) : data_(rhs) {}
+  explicit TraceID(long long rhs) :
+      data_(static_cast<unsigned long long>(rhs)) {}
+  explicit TraceID(long rhs) : data_(static_cast<unsigned long long>(rhs)) {}
+  explicit TraceID(int rhs) : data_(static_cast<unsigned long long>(rhs)) {}
+  explicit TraceID(short rhs) : data_(static_cast<unsigned long long>(rhs)) {}
+  explicit TraceID(signed char rhs) :
+      data_(static_cast<unsigned long long>(rhs)) {}
+
+  unsigned long long data() const { return data_; }
+
+ private:
+  unsigned long long data_;
+};
+
+// Simple union to store various types as unsigned long long.
+union TraceValueUnion {
+  bool as_bool;
+  unsigned long long as_uint;
+  long long as_int;
+  double as_double;
+  const void* as_pointer;
+  const char* as_string;
+};
+
+// Simple container for const char* that should be copied instead of retained.
+class TraceStringWithCopy {
+ public:
+  explicit TraceStringWithCopy(const char* str) : str_(str) {}
+  operator const char* () const { return str_; }
+ private:
+  const char* str_;
+};
+
+// Define SetTraceValue for each allowed type. It stores the type and
+// value in the return arguments. This allows this API to avoid declaring any
+// structures so that it is portable to third_party libraries.
+#define INTERNAL_DECLARE_SET_TRACE_VALUE(actual_type, \
+                                         union_member, \
+                                         value_type_id) \
+    static inline void SetTraceValue(actual_type arg, \
+                                     unsigned char* type, \
+                                     unsigned long long* value) { \
+      TraceValueUnion type_value; \
+      type_value.union_member = arg; \
+      *type = value_type_id; \
+      *value = type_value.as_uint; \
+    }
+// Simpler form for int types that can be safely casted.
+#define INTERNAL_DECLARE_SET_TRACE_VALUE_INT(actual_type, \
+                                             value_type_id) \
+    static inline void SetTraceValue(actual_type arg, \
+                                     unsigned char* type, \
+                                     unsigned long long* value) { \
+      *type = value_type_id; \
+      *value = static_cast<unsigned long long>(arg); \
+    }
+
+INTERNAL_DECLARE_SET_TRACE_VALUE_INT(unsigned long long, TRACE_VALUE_TYPE_UINT)
+INTERNAL_DECLARE_SET_TRACE_VALUE_INT(unsigned int, TRACE_VALUE_TYPE_UINT)
+INTERNAL_DECLARE_SET_TRACE_VALUE_INT(unsigned short, TRACE_VALUE_TYPE_UINT)
+INTERNAL_DECLARE_SET_TRACE_VALUE_INT(unsigned char, TRACE_VALUE_TYPE_UINT)
+INTERNAL_DECLARE_SET_TRACE_VALUE_INT(long long, TRACE_VALUE_TYPE_INT)
+INTERNAL_DECLARE_SET_TRACE_VALUE_INT(int, TRACE_VALUE_TYPE_INT)
+INTERNAL_DECLARE_SET_TRACE_VALUE_INT(short, TRACE_VALUE_TYPE_INT)
+INTERNAL_DECLARE_SET_TRACE_VALUE_INT(signed char, TRACE_VALUE_TYPE_INT)
+INTERNAL_DECLARE_SET_TRACE_VALUE(bool, as_bool, TRACE_VALUE_TYPE_BOOL)
+INTERNAL_DECLARE_SET_TRACE_VALUE(double, as_double, TRACE_VALUE_TYPE_DOUBLE)
+INTERNAL_DECLARE_SET_TRACE_VALUE(const void*, as_pointer,
+                                 TRACE_VALUE_TYPE_POINTER)
+INTERNAL_DECLARE_SET_TRACE_VALUE(const char*, as_string,
+                                 TRACE_VALUE_TYPE_STRING)
+INTERNAL_DECLARE_SET_TRACE_VALUE(const TraceStringWithCopy&, as_string,
+                                 TRACE_VALUE_TYPE_COPY_STRING)
+
+#undef INTERNAL_DECLARE_SET_TRACE_VALUE
+#undef INTERNAL_DECLARE_SET_TRACE_VALUE_INT
+
+// std::string version of SetTraceValue so that trace arguments can be strings.
+static inline void SetTraceValue(const std::string& arg,
+                                 unsigned char* type,
+                                 unsigned long long* value) {
+  TraceValueUnion type_value;
+  type_value.as_string = arg.c_str();
+  *type = TRACE_VALUE_TYPE_COPY_STRING;
+  *value = type_value.as_uint;
+}
+
+// These AddTraceEvent template functions are defined here instead of in the
+// macro, because the arg_values could be temporary objects, such as
+// std::string. In order to store pointers to the internal c_str and pass
+// through to the tracing API, the arg_values must live throughout
+// these procedures.
+
+static inline int AddTraceEvent(char phase,
+                                const unsigned char* category_enabled,
+                                const char* name,
+                                unsigned long long id,
+                                unsigned char flags) {
+  return TRACE_EVENT_API_ADD_TRACE_EVENT(
+      phase, category_enabled, name, id,
+      kZeroNumArgs, NULL, NULL, NULL,
+      kNoThreshholdBeginId, kNoThresholdValue, flags);
+}
+
+template<class ARG1_TYPE>
+static inline int AddTraceEvent(char phase,
+                                const unsigned char* category_enabled,
+                                const char* name,
+                                unsigned long long id,
+                                unsigned char flags,
+                                const char* arg1_name,
+                                const ARG1_TYPE& arg1_val) {
+  const int num_args = 1;
+  unsigned char arg_types[1];
+  unsigned long long arg_values[1];
+  SetTraceValue(arg1_val, &arg_types[0], &arg_values[0]);
+  return TRACE_EVENT_API_ADD_TRACE_EVENT(
+      phase, category_enabled, name, id,
+      num_args, &arg1_name, arg_types, arg_values,
+      kNoThreshholdBeginId, kNoThresholdValue, flags);
+}
+
+template<class ARG1_TYPE, class ARG2_TYPE>
+static inline int AddTraceEvent(char phase,
+                                const unsigned char* category_enabled,
+                                const char* name,
+                                unsigned long long id,
+                                unsigned char flags,
+                                const char* arg1_name,
+                                const ARG1_TYPE& arg1_val,
+                                const char* arg2_name,
+                                const ARG2_TYPE& arg2_val) {
+  const int num_args = 2;
+  const char* arg_names[2] = { arg1_name, arg2_name };
+  unsigned char arg_types[2];
+  unsigned long long arg_values[2];
+  SetTraceValue(arg1_val, &arg_types[0], &arg_values[0]);
+  SetTraceValue(arg2_val, &arg_types[1], &arg_values[1]);
+  return TRACE_EVENT_API_ADD_TRACE_EVENT(
+      phase, category_enabled, name, id,
+      num_args, arg_names, arg_types, arg_values,
+      kNoThreshholdBeginId, kNoThresholdValue, flags);
+}
 
 // Used by TRACE_EVENTx macro. Do not use directly.
 class BASE_EXPORT TraceEndOnScopeClose {
  public:
   // Note: members of data_ intentionally left uninitialized. See Initialize.
   TraceEndOnScopeClose() : p_data_(NULL) {}
   ~TraceEndOnScopeClose() {
     if (p_data_)
       AddEventIfEnabled();
   }
 
-  void Initialize(const TraceCategory* category,
+  void Initialize(const unsigned char* category_enabled,
                   const char* name);
 
  private:
   // Add the end event if the category is still enabled.
   void AddEventIfEnabled();
 
   // This Data struct workaround is to avoid initializing all the members
   // in Data during construction of this object, since this object is always
   // constructed, even when tracing is disabled. If the members of Data were
   // members of this class instead, compiler warnings occur about potential
   // uninitialized accesses.
   struct Data {
-    const TraceCategory* category;
+    const unsigned char* category_enabled;
     const char* name;
   };
   Data* p_data_;
   Data data_;
 };
 
 // Used by TRACE_EVENTx macro. Do not use directly.
 class BASE_EXPORT TraceEndOnScopeCloseThreshold {
  public:
   // Note: members of data_ intentionally left uninitialized. See Initialize.
   TraceEndOnScopeCloseThreshold() : p_data_(NULL) {}
   ~TraceEndOnScopeCloseThreshold() {
     if (p_data_)
       AddEventIfEnabled();
   }
 
   // Called by macros only when tracing is enabled at the point when the begin
   // event is added.
-  void Initialize(const TraceCategory* category,
+  void Initialize(const unsigned char* category_enabled,
                   const char* name,
                   int threshold_begin_id,
-                  int64 threshold);
+                  long long threshold);
 
  private:
   // Add the end event if the category is still enabled.
   void AddEventIfEnabled();
 
   // This Data struct workaround is to avoid initializing all the members
   // in Data during construction of this object, since this object is always
   // constructed, even when tracing is disabled. If the members of Data were
   // members of this class instead, compiler warnings occur about potential
   // uninitialized accesses.
   struct Data {
-    int64 threshold;
-    const TraceCategory* category;
+    long long threshold;
+    const unsigned char* category_enabled;
     const char* name;
     int threshold_begin_id;
   };
   Data* p_data_;
   Data data_;
 };
 
-}  // namespace internal
-
-}  // namespace debug
-}  // namespace base
+}  // namespace trace_event_internal
 
 #endif  // BASE_DEBUG_TRACE_EVENT_H_