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

test/cctest/test-debug.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 4404 matching lines @@
                   ->Int32Value(context)
                   .FromJust());
   CHECK_EQ(2, CompileRun("o0_mirror.property('z').value().value()")
                   ->Int32Value(context)
                   .FromJust());
   CHECK(CompileRun("o0_mirror.property('u').isUndefined()")
             ->BooleanValue(context)
             .FromJust());
 
   // The prototype (__proto__) for o0 should be o3 as o1 and o2 are hidden.
-  CHECK(CompileRun("o0_mirror.protoObject() == o3_mirror")
+  CHECK(CompileRun("o0_mirror.protoObject().value() == o3_mirror.value()")
             ->BooleanValue(context)
             .FromJust());
 }
 
 
 static void ProtperyXNativeGetter(
     v8::Local<v8::String> property,
     const v8::PropertyCallbackInfo<v8::Value>& info) {
   info.GetReturnValue().Set(10);
 }
@@ skipping 2216 matching lines @@
                                       reinterpret_cast<void*>(isolate));
     CHECK(!out_of_memory_callback_called);
     // The following allocation fails unless the out-of-memory callback
     // increases the heap limit.
     int length = 10 * i::MB / i::kPointerSize;
     i_isolate->factory()->NewFixedArray(length, i::TENURED);
     CHECK(out_of_memory_callback_called);
   }
   isolate->Dispose();
 }