Simplify the canonicalization of dart-ext uris.

runtime/bin/dartutils.h

Index: runtime/bin/dartutils.h
diff --git a/runtime/bin/dartutils.h b/runtime/bin/dartutils.h
index ed63c7cadec0f87213ca5fb0d29af518e7686cdc..b416a9399cf76dd9c42d30db5dd060a7e763c4a1 100644
--- a/runtime/bin/dartutils.h
+++ b/runtime/bin/dartutils.h
@@ -115,6 +115,7 @@ class DartUtils {
   static bool IsDartIOLibURL(const char* url_name);
   static bool IsDartBuiltinLibURL(const char* url_name);
   static bool IsHttpSchemeURL(const char* url_name);
+  static const char* RemoveScheme(const char* url);
   static void* MapExecutable(const char* name, intptr_t* file_len);
   static void* OpenFile(const char* name, bool write);
   static void ReadFile(const uint8_t** data, intptr_t* file_len, void* stream);
@@ -232,8 +233,7 @@ class DartUtils {
 
  private:
   static Dart_Handle SetWorkingDirectory();
-  static Dart_Handle ExtensionPathFromUri(Dart_Handle extension_uri);
-
+  static Dart_Handle LibraryFilePath(Dart_Handle library_uri);
   static Dart_Handle PrepareBuiltinLibrary(Dart_Handle builtin_lib,
                                            Dart_Handle internal_lib,
                                            bool is_service_isolate,