Added Dart API methods:

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
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  * \param arg_index Index of the desired argument in the structure above.
  * \param peer Returns the peer pointer if the String is an external String.
  * \return the String object if no error occurs. Otherwise returns
  *   an error handle.
  */
 DART_EXPORT Dart_Handle Dart_GetNativeStringArgument(Dart_NativeArguments args,
                                                      int arg_index,
                                                      void** peer);
 
 /**
+ * Gets an integer native argument at some index.
+ * \param args Native arguments structure.
+ * \param arg_index Index of the desired argument in the structure above.
+ * \param value Returns the integer value if the argument is an Integer.
+ * \return Success if no error occurs. Otherwise returns an error handle.
+ */
+DART_EXPORT Dart_Handle Dart_GetNativeIntegerArgument(Dart_NativeArguments args,
+                                                      int index,
+                                                      int64_t* value);
+
+/**
+ * Gets a boolean native argument at some index.
+ * \param args Native arguments structure.
+ * \param arg_index Index of the desired argument in the structure above.
+ * \param value Returns the boolean value if the argument is a Boolean.
+ * \return Success if no error occurs. Otherwise returns an error handle.
+ */
+DART_EXPORT Dart_Handle Dart_GetNativeBooleanArgument(Dart_NativeArguments args,
+                                                      int index,
+                                                      bool* value);
+
+/**
+ * Gets a double native argument at some index.
+ * \param args Native arguments structure.
+ * \param arg_index Index of the desired argument in the structure above.
+ * \param value Returns the double value if the argument is a double.
+ * \return Success if no error occurs. Otherwise returns an error handle.
+ */
+DART_EXPORT Dart_Handle Dart_GetNativeDoubleArgument(Dart_NativeArguments args,
+                                                     int index,
+                                                     double* value);
+
+/**
  * Sets the return value for a native function.
  */
 DART_EXPORT void Dart_SetReturnValue(Dart_NativeArguments args,
                                      Dart_Handle retval);
 
 DART_EXPORT void Dart_SetWeakHandleReturnValue(Dart_NativeArguments args,
                                                Dart_WeakPersistentHandle rval);
 
 DART_EXPORT void Dart_SetBooleanReturnValue(Dart_NativeArguments args,
                                             bool retval);
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  *
  * \param object An object.
  * \param peer A value to store in the peer field.
  *
  * \return Returns an error if 'object' is a subtype of Null, num, or
  *   bool.
  */
 DART_EXPORT Dart_Handle Dart_SetPeer(Dart_Handle object, void* peer);
 
 #endif  /* INCLUDE_DART_API_H_ */  /* NOLINT */