Only reload libraries when they may have been modified.

runtime/vm/unit_test.h

 // Copyright (c) 2011, 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 VM_UNIT_TEST_H_
 #define VM_UNIT_TEST_H_
 
 #include "include/dart_native_api.h"
 
 #include "platform/globals.h"
@@ skipping 296 matching lines @@
   // Sets |script| to be the source used at next reload.
   static void SetReloadTestScript(const char* script);
   // Initiates the reload.
   static Dart_Handle TriggerReload();
   // Gets the result of a reload.
   static Dart_Handle GetReloadErrorOrRootLibrary();
 
   // Helper function which reloads the current isolate using |script|.
   static Dart_Handle ReloadTestScript(const char* script);
 
+  // Changes the default importable test lib script.
+  static void SetImportableTestLibScript(const char* source);
+  static void RestoreImportableTestLibScript();
+
  private:
   static Dart_Isolate CreateIsolate(const uint8_t* buffer, const char* name);
 
   RunEntry* const run_;
 };
 
 
 class TestIsolateScope {
  public:
   TestIsolateScope() {
@@ skipping 282 matching lines @@
   }
 
  private:
   T* flag_;
   T original_value_;
 };
 
 }  // namespace dart
 
 #endif  // VM_UNIT_TEST_H_