Use chromium trace_event implementation in blink

base/trace_event/trace_event.h

 // Copyright (c) 2012 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.
 
 #ifndef BASE_TRACE_EVENT_TRACE_EVENT_H_
 #define BASE_TRACE_EVENT_TRACE_EVENT_H_
 
 // 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_event_common.h instead of here.
@@ skipping 46 matching lines @@
 // thread from others.
 #define TRACE_EVENT_SET_SAMPLING_STATE_FOR_BUCKET( \
     bucket_number, category, name)                 \
         trace_event_internal::                     \
         TraceEventSamplingStateScope<bucket_number>::Set(category "\0" name)
 
 // Returns a current sampling state of the given bucket.
 #define TRACE_EVENT_GET_SAMPLING_STATE_FOR_BUCKET(bucket_number) \
     trace_event_internal::TraceEventSamplingStateScope<bucket_number>::Current()
 
+// Sets a current sampling state of the given bucket.
+// |categoryAndName| doesn't need to be a constant string.

[oystein (OOO til 10th of July), 2016/09/20 18:11:17]

nit: category_and_name

[Xianzhu, 2016/09/20 18:15:47]

Done.

+// The format of the string is "category\0name".
+#define TRACE_EVENT_SET_NONCONST_SAMPLING_STATE_FOR_BUCKET( \
+    bucket_number, category_and_name)                       \
+        trace_event_internal::                              \
+        TraceEventSamplingStateScope<bucket_number>::Set(category_and_name)
+
 // Creates a scope of a sampling state of the given bucket.
 //
 // {  // The sampling state is set within this scope.
 //    TRACE_EVENT_SAMPLING_STATE_SCOPE_FOR_BUCKET(0, "category", "name");
 //    ...;
 // }
 #define TRACE_EVENT_SCOPED_SAMPLING_STATE_FOR_BUCKET(                   \
     bucket_number, category, name)                                      \
     trace_event_internal::TraceEventSamplingStateScope<bucket_number>   \
         traceEventSamplingScope(category "\0" name);
@@ skipping 1080 matching lines @@
   const char* name_;
   IDType id_;
 
   DISALLOW_COPY_AND_ASSIGN(TraceScopedTrackableObject);
 };
 
 }  // namespace trace_event
 }  // namespace base
 
 #endif  // BASE_TRACE_EVENT_TRACE_EVENT_H_