Do not use C++ const references in the C interface.

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 84 matching lines @@
  */
 typedef struct _Dart_Handle* Dart_Handle;
 
 typedef void (*Dart_PeerFinalizer)(void* peer);
 
 /**
  * Is this an error handle?
  *
  * Requires there to be a current isolate.
  */
-DART_EXPORT bool Dart_IsError(const Dart_Handle& handle);
+DART_EXPORT bool Dart_IsError(Dart_Handle handle);
 
 /**
  * Gets the error message from an error handle.
  *
  * Requires there to be a current isolate.
  *
  * \return A C string containing an error message if the handle is
  *   error. 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);
+DART_EXPORT const char* Dart_GetError(Dart_Handle handle);
 
 /**
  * Is this an error handle for an unhandled exception?
  */
 DART_EXPORT bool Dart_ErrorHasException(Dart_Handle handle);
 
 /**
  * Gets the exception Object from an unhandled exception error handle.
  */
 DART_EXPORT Dart_Handle Dart_ErrorGetException(Dart_Handle handle);
@@ skipping 1253 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_