Revert of [debugger] deprecate v8::Debug:GetDebugContext.

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 230 matching lines @@
   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.
    */
-  V8_DEPRECATED("Use v8-inspector",
-                static Local<Context> GetDebugContext(Isolate* isolate));
+  static Local<Context> GetDebugContext(Isolate* isolate);
 
   /**
    * While in the debug context, this method returns the top-most non-debug
    * context, if it exists.
    */
   V8_DEPRECATED(
       "No longer supported",
       static MaybeLocal<Context> GetDebuggedContext(Isolate* isolate));
 
   /**
@@ skipping 21 matching lines @@
 };
 
 
 }  // namespace v8
 
 
 #undef EXPORT
 
 
 #endif  // V8_V8_DEBUG_H_