Add Dart_PropagateError.

runtime/include/dart_api.h

 // Copyright (c) 2012, 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 122 matching lines @@
 
 /**
  * Produces an error handle with the provided error message.
  *
  * Requires there to be a current isolate.
  *
  * \param error A C string containing an error message.
  */
 DART_EXPORT Dart_Handle Dart_Error(const char* format, ...);
 
+/**
+ * Propagates an error.
+ *
+ * It only makes sense to call this function when there are dart
+ * frames on the stack.  That is, this function should only be called
+ * in the C implementation of a native function which has been called
+ * from Dart code.  If this function is called in the top-level
+ * embedder code, it will return an error, as there is no way to
+ * further propagate the error.
+ *
+ * The provided handle must be an error handle.  (See Dart_IsError.)
+ *
+ * If the provided handle is an unhandled exception, this function
+ * will cause the unhandled exception to be rethrown.  Otherwise, the
+ * error will be propagated to the caller, discarding any active dart
+ * frames up to the next C frame.
+ *
+ * \param An error handle.
+ *
+ * \return On success, this function does not return.  On failure, an
+ *   error handle is returned.
+ */
+DART_EXPORT Dart_Handle Dart_PropagateError(Dart_Handle handle);
+
 // Internal routine used for reporting error handles.
 DART_EXPORT void _Dart_ReportErrorHandle(const char* file,
                                          int line,
                                          const char* handle_string,
                                          const char* error);
 
 // TODO(turnidge): Move DART_CHECK_VALID to some sort of dart_utils
 // header instead of this header.
 /**
  * Aborts the process if 'handle' is an error handle.
@@ skipping 1284 matching lines @@
 };
 
 /**
  * A Dart_CMessage is used for encoding and decoding messages from native code.
  */
 struct Dart_CMessage {
   Dart_CObject** message;
 };
 
 #endif  // INCLUDE_DART_API_H_