Make down-conversion explicit from CFX_ByteString to CFX_ByteStringC.

core/fpdfapi/fpdf_page/fpdf_page_doc.cpp

Index: core/fpdfapi/fpdf_page/fpdf_page_doc.cpp
diff --git a/core/fpdfapi/fpdf_page/fpdf_page_doc.cpp b/core/fpdfapi/fpdf_page/fpdf_page_doc.cpp
index 9f4ad5a7d52f86310d9a5ced50c0629492d5b3ad..758ce940d298f6bf6761af3a654b37a9862ac511 100644
--- a/core/fpdfapi/fpdf_page/fpdf_page_doc.cpp
+++ b/core/fpdfapi/fpdf_page/fpdf_page_doc.cpp
@@ -331,7 +331,7 @@ CPDF_ColorSpace* CPDF_DocPageData::GetColorSpace(
     if (!pCS && pResources) {
       CPDF_Dictionary* pList = pResources->GetDictBy("ColorSpace");
       if (pList) {
-        pCSObj = pList->GetDirectObjectBy(name);
+        pCSObj = pList->GetDirectObjectBy(name.AsByteStringC());
         return GetColorSpace(pCSObj, nullptr);
       }
     }