[DevTools] Handle emulated device scale factor and original device scale factor properly.

content/common/content_switches_internal.h

 // Copyright (c) 2014 The Chromium 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 CONTENT_COMMON_CONTENT_SWITCHES_INTERNAL_H_
 #define CONTENT_COMMON_CONTENT_SWITCHES_INTERNAL_H_
 
 #include "build/build_config.h"
+#include "content/common/content_export.h"
 #include "content/public/common/web_preferences.h"
 
 namespace content {
 
 bool IsPinchToZoomEnabled();
 #if defined(OS_WIN)
 // Disables Win32k Renderer lockdown for any future renderer child processes.
 void DisableWin32kRendererLockdown();
 
 // Returns whether Win32k Renderer lockdown is enabled or not.
 bool IsWin32kRendererLockdownEnabled();
 #endif
 V8CacheOptions GetV8CacheOptions();
 
-bool IsUseZoomForDSFEnabled();
+CONTENT_EXPORT bool IsUseZoomForDSFEnabled();
 
 } // namespace content
 
 #endif  // CONTENT_COMMON_CONTENT_SWITCHES_INTERNAL_H_