Allow printf-style arguments for Dart_Error and Api::Error.

runtime/include/dart_api.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 INCLUDE_DART_API_H_
 #define INCLUDE_DART_API_H_
 
 /** \mainpage Dart Embedding API Reference
  *
  * Dart is a class-based programming language for creating structured
@@ skipping 102 matching lines @@
  * \return A C string containing an error message if the handle is
  *   invalid. An empty C string ("") if the handle is valid.  This C
  *   String is scope allocated and is only valid until the next call
  *   to Dart_ExitScope.
 */
 DART_EXPORT const char* Dart_GetError(const Dart_Handle& handle);
 
 /**
  * Produces an invalid handle with the provided error message.
  *
- * This function makes its own copy of the error message and does not
- * claim ownership of the 'error' parameter.
- *
  * Requires there to be a current isolate.
  *
  * \param error A C string containing an error message.
  */
-DART_EXPORT Dart_Handle Dart_Error(const char* error);
-// TODO(turnidge): Accept printf-style args here.
+DART_EXPORT Dart_Handle Dart_Error(const char* format, ...);
 
 /**
  * Allocates a persistent handle for an object.
  *
  * This handle has the lifetime of the current isolate unless it is
  * explicitly deallocated by calling Dart_DeletePersistentHandle.
  *
  * Requires there to be a current isolate.
  */
 DART_EXPORT Dart_Handle Dart_NewPersistentHandle(Dart_Handle object);
@@ skipping 993 matching lines @@
 
 // --- Profiling support ----
 
 // External pprof support for gathering and dumping symbolic
 // information that can be used for better profile reports for
 // dynamically generated code.
 DART_EXPORT void Dart_InitPprofSupport();
 DART_EXPORT void Dart_GetPprofSymbolInfo(void** buffer, int* buffer_size);
 
 #endif  // INCLUDE_DART_API_H_