c_str() calls not needed when writing to ostream

c_str() is a bit of a code smell, esp. since Byte/Wide strings
know how to do this all by themselves.

Change-Id: I9c86cee42c12a3f72ddb1d410a91cf25647d0ce6
Reviewed-on: https://pdfium-review.googlesource.com/35530
Commit-Queue: dsinclair <dsinclair@chromium.org>
Reviewed-by: dsinclair <dsinclair@chromium.org>
diff --git a/fpdfsdk/cpdfsdk_interform.cpp b/fpdfsdk/cpdfsdk_interform.cpp
index 379a8b9..751a889 100644
--- a/fpdfsdk/cpdfsdk_interform.cpp
+++ b/fpdfsdk/cpdfsdk_interform.cpp
@@ -515,7 +515,7 @@
     ByteString csBValue = pField->GetStringFor("V");
     WideString csWValue = PDF_DecodeText(csBValue);
     ByteString csValue_b = ByteString::FromUnicode(csWValue);
-    fdfEncodedData << name_b.c_str() << "=" << csValue_b.c_str();
+    fdfEncodedData << name_b << "=" << csValue_b;
     if (i != pFields->GetCount() - 1)
       fdfEncodedData << "&";
   }