[gn] Enable stricter build flags

test/inspector/inspector-test.cc

 // Copyright 2016 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.
 
 #if !defined(_WIN32) && !defined(_WIN64)
 #include <unistd.h>  // NOLINT
 #endif               // !defined(_WIN32) && !defined(_WIN64)
 
 #include <locale.h>
 
@@ skipping 270 matching lines @@
     inspector_client_->session()->schedulePauseOnNextStatement(reason_view,
                                                                details_view);
   }
 
   static void CancelPauseOnNextStatement(
       const v8::FunctionCallbackInfo<v8::Value>& args) {
     if (args.Length() != 0) {
       fprintf(stderr, "Internal error: cancelPauseOnNextStatement().");
       Exit();
     }
-    v8::Local<v8::Context> context = args.GetIsolate()->GetCurrentContext();
     inspector_client_->session()->cancelPauseOnNextStatement();
   }
 
   static void Reconnect(const v8::FunctionCallbackInfo<v8::Value>& args) {
     if (args.Length() != 0) {
       fprintf(stderr, "Internal error: reconnect().");
       Exit();
     }
     v8::base::Semaphore ready_semaphore(0);
     inspector_client_->scheduleReconnect(&ready_semaphore);
@@ skipping 382 matching lines @@
               argv[i]);
       Exit();
     }
     frontend_runner.Append(new ExecuteStringTask(chars));
   }
 
   frontend_runner.Join();
   backend_runner.Join();
   return 0;
 }