[debugger] remove mirror cache and v8::Debug::GetMirror.

src/debug/debug.js

 // Copyright 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.
 
 (function (global, utils) {
 "use strict";
 
 // ----------------------------------------------------------------------------
 // Imports
 
 var FrameMirror = global.FrameMirror;
 var GlobalArray = global.Array;
 var GlobalRegExp = global.RegExp;
 var IsNaN = global.isNaN;
-var LookupMirror = global.LookupMirror;
 var MakeMirror = global.MakeMirror;
 var MathMin = global.Math.min;
 var Mirror = global.Mirror;
 var MirrorType;
 var ParseInt = global.parseInt;

[jgruber, 2017/02/02 12:17:16]

MirrorType and ParseInt also seem to be unused.

 var ValueMirror = global.ValueMirror;
 
 utils.Import(function(from) {
   MirrorType = from.MirrorType;
 });
 
 //----------------------------------------------------------------------------
 
 // Default number of frames to include in the response to backtrace request.
 var kDefaultBacktraceLength = 10;
@@ skipping 997 matching lines @@
 utils.InstallFunctions(utils, DONT_ENUM, [
   "MakeExecutionState", MakeExecutionState,
   "MakeExceptionEvent", MakeExceptionEvent,
   "MakeBreakEvent", MakeBreakEvent,
   "MakeCompileEvent", MakeCompileEvent,
   "MakeAsyncTaskEvent", MakeAsyncTaskEvent,
   "IsBreakPointTriggered", IsBreakPointTriggered,
 ]);
 
 })