1. Add flag --trace-api to trace API function invocation

runtime/vm/native_entry.cc

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/native_entry.h"
 
 #include "include/dart_api.h"
 
 #include "vm/dart_api_impl.h"
 #include "vm/dart_api_state.h"
@@ skipping 35 matching lines @@
 void NativeEntry::NativeCallWrapper(Dart_NativeArguments args,
                                     Dart_NativeFunction func) {
   CHECK_STACK_ALIGNMENT;
   VERIFY_ON_TRANSITION;
   NativeArguments* arguments = reinterpret_cast<NativeArguments*>(args);
   Isolate* isolate = arguments->isolate();
   ApiState* state = isolate->api_state();
   ASSERT(state != NULL);
   ApiLocalScope* current_top_scope = state->top_scope();
   ApiLocalScope* scope = state->reusable_scope();
+  TRACE_NATIVES("0x%" Px "", reinterpret_cast<uintptr_t>(func));
   if (scope == NULL) {
     scope = new ApiLocalScope(current_top_scope,
                               isolate->top_exit_frame_info());
     ASSERT(scope != NULL);
   } else {
     scope->Reinit(isolate,
                   current_top_scope,
                   isolate->top_exit_frame_info());
     state->set_reusable_scope(NULL);
   }
   state->set_top_scope(scope);  // New scope is now the top scope.
 
   func(args);
 
   ASSERT(current_top_scope == scope->previous());
   state->set_top_scope(current_top_scope);  // Reset top scope to previous.
   if (state->reusable_scope() == NULL) {
     scope->Reset(isolate);  // Reset the old scope which we just exited.
     state->set_reusable_scope(scope);
   } else {
     ASSERT(state->reusable_scope() != scope);
     delete scope;
   }
   DEOPTIMIZE_ALOT;
   VERIFY_ON_TRANSITION;
 }
 
 }  // namespace dart