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

src/debug/debug.h

 // 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.
 
 #ifndef V8_DEBUG_DEBUG_H_
 #define V8_DEBUG_DEBUG_H_
 
 #include "src/allocation.h"
 #include "src/arguments.h"
 #include "src/assembler.h"
@@ skipping 483 matching lines @@
       Handle<Object> break_points_hit);
   MUST_USE_RESULT MaybeHandle<Object> MakeExceptionEvent(
       Handle<Object> exception,
       bool uncaught,
       Handle<Object> promise);
   MUST_USE_RESULT MaybeHandle<Object> MakeCompileEvent(
       Handle<Script> script, v8::DebugEvent type);
   MUST_USE_RESULT MaybeHandle<Object> MakeAsyncTaskEvent(Handle<Smi> type,
                                                          Handle<Smi> id);
 
-  // Mirror cache handling.
-  void ClearMirrorCache();
-
   void ProcessCompileEvent(v8::DebugEvent event, Handle<Script> script);
   void ProcessDebugEvent(v8::DebugEvent event, Handle<JSObject> event_data);
 
   // Find the closest source position for a break point for a given position.
   int FindBreakablePosition(Handle<DebugInfo> debug_info, int source_position,
                             BreakPositionAlignment alignment);
   // Instrument code to break at break points.
   void ApplyBreakPoints(Handle<DebugInfo> debug_info);
   // Clear code from instrumentation.
   void ClearBreakPoints(Handle<DebugInfo> debug_info);
@@ skipping 223 matching lines @@
                                   Handle<Code> code);
   static bool DebugBreakSlotIsPatched(Address pc);
   static void ClearDebugBreakSlot(Isolate* isolate, Address pc);
 };
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_DEBUG_DEBUG_H_