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

runtime/vm/native_entry.h

 // 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.
 
 #ifndef VM_NATIVE_ENTRY_H_
 #define VM_NATIVE_ENTRY_H_
 
 #include "vm/allocation.h"
 #include "vm/assembler.h"
 #include "vm/code_generator.h"
@@ skipping 25 matching lines @@
 #endif
 
 #define DEFINE_NATIVE_ENTRY(name, argument_count)                              \
   static RawObject* DN_Helper##name(Isolate* isolate,                          \
                                     NativeArguments* arguments);               \
   void NATIVE_ENTRY_FUNCTION(name)(Dart_NativeArguments args) {                \
     CHECK_STACK_ALIGNMENT;                                                     \
     VERIFY_ON_TRANSITION;                                                      \
     NativeArguments* arguments = reinterpret_cast<NativeArguments*>(args);     \
     ASSERT(arguments->NativeArgCount() == argument_count);                     \
-    TRACE_NATIVES(""#name);                                                    \
+    TRACE_NATIVES("%s", ""#name);                                              \
     {                                                                          \
       StackZone zone(arguments->isolate());                                    \
       SET_NATIVE_RETVAL(arguments,                                             \
                         DN_Helper##name(arguments->isolate(), arguments));     \
       DEOPTIMIZE_ALOT;                                                         \
     }                                                                          \
     VERIFY_ON_TRANSITION;                                                      \
   }                                                                            \
   static RawObject* DN_Helper##name(Isolate* isolate,                          \
                                     NativeArguments* arguments)
@@ skipping 38 matching lines @@
                                       const String& function_name,
                                       int number_of_arguments);
   static void NativeCallWrapper(Dart_NativeArguments args,
                                 Dart_NativeFunction func);
   static const ExternalLabel& NativeCallWrapperLabel();
 };
 
 }  // namespace dart
 
 #endif  // VM_NATIVE_ENTRY_H_