Remove implicit cast from CFX_ByteString to (const char*).

core/fpdfdoc/doc_form.cpp

Index: core/fpdfdoc/doc_form.cpp
diff --git a/core/fpdfdoc/doc_form.cpp b/core/fpdfdoc/doc_form.cpp
index 207b82454566d81eba98e8dd00a056ba172063c1..6ca40fdaf6c0ae7bf6b61c2b5c4c32c6f810bee4 100644
--- a/core/fpdfdoc/doc_form.cpp
+++ b/core/fpdfdoc/doc_form.cpp
@@ -633,11 +633,11 @@ FX_BOOL CPDF_InterForm::ValidateFieldName(const CPDF_FormControl* pControl,
 }
 int CPDF_InterForm::CompareFieldName(const CFX_ByteString& name1,
                                      const CFX_ByteString& name2) {
-  const FX_CHAR* ptr1 = name1;
-  const FX_CHAR* ptr2 = name2;
   if (name1.GetLength() == name2.GetLength()) {
     return name1 == name2 ? 1 : 0;
   }
+  const FX_CHAR* ptr1 = name1.c_str();
+  const FX_CHAR* ptr2 = name2.c_str();
   int i = 0;
   while (ptr1[i] == ptr2[i]) {
     i++;