Rename CFX_RetainPtr to RetainPtr

This CL renames CFX_RetainPtr to RetainPtr and places in the fxcrt
namespace.

Bug: pdfium:898
Change-Id: I8798a9f79cb0840d3f037e8d04937cedd742914e
Reviewed-on: https://pdfium-review.googlesource.com/14616
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Commit-Queue: dsinclair <dsinclair@chromium.org>
diff --git a/fxbarcode/BC_Writer.h b/fxbarcode/BC_Writer.h
index fc98a4c..565c03f 100644
--- a/fxbarcode/BC_Writer.h
+++ b/fxbarcode/BC_Writer.h
@@ -25,7 +25,7 @@
   virtual void SetBarcodeColor(FX_ARGB foregroundColor);
 
  protected:
-  CFX_RetainPtr<CFX_DIBitmap> CreateDIBitmap(int32_t width, int32_t height);
+  RetainPtr<CFX_DIBitmap> CreateDIBitmap(int32_t width, int32_t height);
   int32_t m_CharEncoding;
   int32_t m_ModuleHeight;
   int32_t m_ModuleWidth;