Add attributions so printf like functions can have their arguments checked.

runtime/vm/dart_api_impl.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_DART_API_IMPL_H_
 #define VM_DART_API_IMPL_H_
 
 #include "vm/allocation.h"
 #include "vm/object.h"
 
@@ skipping 117 matching lines @@
   static intptr_t ClassId(Dart_Handle handle) {
     // TODO(turnidge): Assumes RawObject* is at offset zero.  Fix.
     RawObject* raw = *(reinterpret_cast<RawObject**>(handle));
     if (!raw->IsHeapObject()) {
       return kSmiCid;
     }
     return raw->GetClassId();
   }
 
   // Generates a handle used to designate an error return.
-  static Dart_Handle NewError(const char* format, ...);
+  static Dart_Handle NewError(const char* format, ...) PRINTF_ATTRIBUTE(1, 2);
 
   // Gets a handle to Null.
   static Dart_Handle Null(Isolate* isolate);
 
   // Gets a handle to True.
   static Dart_Handle True(Isolate* isolate);
 
   // Gets a handle to False
   static Dart_Handle False(Isolate* isolate);
 
@@ skipping 24 matching lines @@
   }
  private:
   Isolate* saved_isolate_;
 
   DISALLOW_COPY_AND_ASSIGN(IsolateSaver);
 };
 
 }  // namespace dart.
 
 #endif  // VM_DART_API_IMPL_H_