Mark CFX_RenderDevice ctor as protected.

CFX_RenderDevice is a base class and thus should not be directly
instantiated.

Change-Id: I7e60cf75e2c27e2536fb502bda389a02cee86d93
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/70190
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>
diff --git a/core/fxge/cfx_renderdevice.h b/core/fxge/cfx_renderdevice.h
index 755f445..56e9329 100644
--- a/core/fxge/cfx_renderdevice.h
+++ b/core/fxge/cfx_renderdevice.h
@@ -40,7 +40,6 @@
     UnownedPtr<CFX_RenderDevice> m_pDevice;
   };
 
-  CFX_RenderDevice();
   virtual ~CFX_RenderDevice();
 
   static CFX_Matrix GetFlipMatrix(float width,
@@ -222,6 +221,9 @@
   void Flush(bool release);
 #endif
 
+ protected:
+  CFX_RenderDevice();
+
  private:
   void InitDeviceInfo();
   void UpdateClipBox();