Fix typo from commit r447946588d6b.

TBR=tsepez@chromium.org

Review URL: https://codereview.chromium.org/1452843005 .
diff --git a/core/src/fpdfdoc/doc_form.cpp b/core/src/fpdfdoc/doc_form.cpp
index 93d4fcb..241609e 100644
--- a/core/src/fpdfdoc/doc_form.cpp
+++ b/core/src/fpdfdoc/doc_form.cpp
@@ -517,7 +517,7 @@
   CFX_ByteString csFontName = GetNativeFont(charSet, &lf);
   if (!csFontName.IsEmpty()) {
     if (csFontName == "Helvetica")
-      return pFont = AddStandardFont(pDocument, csFontName);
+      return AddStandardFont(pDocument, csFontName);
     return pDocument->AddWindowsFont(&lf, FALSE, TRUE);
   }
 #endif