Add patch file support to Dart embedder

mojo/dart/embedder/builtin.h

Index: mojo/dart/embedder/builtin.h
diff --git a/mojo/dart/embedder/builtin.h b/mojo/dart/embedder/builtin.h
index bce0c3e95fc38b976c399ad23e94044a9b2c3aec..aa2d0d5b41c0be4aaca20c58b8e3fe8022a188c7 100644
--- a/mojo/dart/embedder/builtin.h
+++ b/mojo/dart/embedder/builtin.h
@@ -56,15 +56,21 @@ class Builtin {
                                           bool* auto_setup_scope);
 
   static const uint8_t* NativeSymbol(Dart_NativeFunction nf);
-
+  static Dart_Handle ReadStringFromFile(const char* file);
+  static void LoadPatchFiles(Dart_Handle library,
+                             const char* patch_uri,
+                             const char** patch_files);
   typedef struct {
     const char* url_;
     bool has_natives_;
     Dart_NativeEntrySymbol native_symbol_;
     Dart_NativeEntryResolver native_resolver_;
+    const char* patch_url_;
+    const char** patch_paths_;
   } builtin_lib_props;
   static builtin_lib_props builtin_libraries_[];
 
+  static const char* mojo_core_patch_paths_[];
   DISALLOW_IMPLICIT_CONSTRUCTORS(Builtin);
 };