Refactor native extension shared library lookup.

runtime/bin/dartutils.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 BIN_DARTUTILS_H_
 #define BIN_DARTUTILS_H_
 
 #include "include/dart_api.h"
 #include "include/dart_native_api.h"
 
@@ skipping 167 matching lines @@
                                    const char* url_string);
 
   static Dart_Handle SetWorkingDirectory(Dart_Handle builtin_lib);
 
   static Dart_Handle ResolveScriptUri(Dart_Handle script_uri,
                                       Dart_Handle builtin_lib);
 
   static Dart_Handle FilePathFromUri(Dart_Handle script_uri,
                                      Dart_Handle builtin_lib);
 
+  static Dart_Handle ExtensionPathFromUri(Dart_Handle extension_uri,
+                                          Dart_Handle builtin_lib);
+
   static Dart_Handle ResolveUri(Dart_Handle library_url,
                                 Dart_Handle url,
                                 Dart_Handle builtin_lib);
 
   // Sniffs the specified text_buffer to see if it contains the magic number
   // representing a script snapshot. If the text_buffer is a script snapshot
   // the return value is an updated pointer to the text_buffer pointing past
   // the magic number value. The 'buffer_len' parameter is also appropriately
   // adjusted.
   static const uint8_t* SniffForMagicNumber(const uint8_t* text_buffer,
@@ skipping 344 matching lines @@
   }
 
  private:
   DISALLOW_COPY_AND_ASSIGN(CObjectExternalUint8Array);
 };
 
 }  // namespace bin
 }  // namespace dart
 
 #endif  // BIN_DARTUTILS_H_