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

include/v8-debug.h

 // Copyright 2008 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.
 
 #ifndef V8_V8_DEBUG_H_
 #define V8_V8_DEBUG_H_
 
 #include "v8.h"  // NOLINT(build/include)
 
 /**
@@ skipping 176 matching lines @@
    *   function frame_source_line(exec_state) {
    *     return exec_state.frame(0).sourceLine();
    *   }
    * \endcode
    */
   // TODO(dcarney): data arg should be a MaybeLocal
   static MaybeLocal<Value> Call(Local<Context> context,
                                 v8::Local<v8::Function> fun,
                                 Local<Value> data = Local<Value>());
 
-  /**
-   * Returns a mirror object for the given object.
-   */
-  V8_DEPRECATED("No longer supported",
-                static MaybeLocal<Value> GetMirror(Local<Context> context,
-                                                   v8::Local<v8::Value> obj));
-
   // This is now a no-op.
   V8_DEPRECATED("No longer supported",
                 static void ProcessDebugMessages(Isolate* isolate));
 
   /**
    * Debugger is running in its own context which is entered while debugger
    * messages are being dispatched. This is an explicit getter for this
    * debugger context. Note that the content of the debugger context is subject
    * to change. The Context exists only when the debugger is active, i.e. at
    * least one DebugEventListener or MessageHandler is set.
@@ skipping 34 matching lines @@
 };
 
 
 }  // namespace v8
 
 
 #undef EXPORT
 
 
 #endif  // V8_V8_DEBUG_H_