Re-enable Dart_Api Timeline tracing

runtime/vm/dart_api_impl.cc

Index: runtime/vm/dart_api_impl.cc
diff --git a/runtime/vm/dart_api_impl.cc b/runtime/vm/dart_api_impl.cc
index 796aaca89d032a40788d4cbc791d7e3b23635dca..162d2fd250b12bd157b8786d78de995e00ad4348 100644
--- a/runtime/vm/dart_api_impl.cc
+++ b/runtime/vm/dart_api_impl.cc
@@ -77,7 +77,6 @@ const char* CanonicalFunction(const char* func) {
   }
 }
 
-#if 0
 #define API_TIMELINE_DURATION                                                  \
   TimelineDurationScope tds(Thread::Current(),                                 \
                             Timeline::GetVMApiStream(),                        \
@@ -87,10 +86,7 @@ const char* CanonicalFunction(const char* func) {
   TimelineBeginEndScope tbes(Thread::Current(),                                \
                              Timeline::GetVMApiStream(),                       \
                              CURRENT_FUNC)
-#else
-#define API_TIMELINE_DURATION ASSERT(true)
-#define API_TIMELINE_BEGIN_END ASSERT(true)
-#endif
+
 
 #if defined(DEBUG)
 // An object visitor which will iterate over all the function objects in the