Do not clear mirror cache when fetching loaded scripts.

src/mirror-debugger.js

 // Copyright 2006-2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Handle id counters.
 var next_handle_ = 0;
 var next_transient_handle_ = -1;
 
 // Mirror cache.
 var mirror_cache_ = [];
 var mirror_cache_enabled_ = true;
 
 
 function ToggleMirrorCache(value) {
   mirror_cache_enabled_ = value;
   next_handle_ = 0;
   mirror_cache_ = [];
 }
 
 
-/**
- * Clear the mirror handle cache.
- */
-function ClearMirrorCache() {
-  next_handle_ = 0;
-  mirror_cache_ = [];
-}
-
-
 // Wrapper to check whether an object is a Promise.  The call may not work
 // if promises are not enabled.
 // TODO(yangguo): remove try-catch once promises are enabled by default.
 function ObjectIsPromise(value) {
   try {
     return IS_SPEC_OBJECT(value) &&
            !IS_UNDEFINED(%DebugGetProperty(value, builtins.promiseStatus));
   } catch (e) {
     return false;
   }
@@ skipping 2746 matching lines @@
   }
   if (!NUMBER_IS_FINITE(value)) {
     if (value > 0) {
       return 'Infinity';
     } else {
       return '-Infinity';
     }
   }
   return value;
 }