Merge to XFA: Add type cast definitions for CPDF_Name.

This Cl adds ToName, CPDF_Object::AsName and CPDF_Object::IsName and
updates the src to use them as needed.

BUG=pdfium:201
R=tsepez@chromium.org

Review URL: https://codereview.chromium.org/1417823005 .

(cherry picked from commit 1c77edb7b34e03787605b7965784cea38ef9f1d7)

Review URL: https://codereview.chromium.org/1417033004 .
diff --git a/core/src/fpdfdoc/doc_formfield.cpp b/core/src/fpdfdoc/doc_formfield.cpp
index 7e734b4..0766eb0 100644
--- a/core/src/fpdfdoc/doc_formfield.cpp
+++ b/core/src/fpdfdoc/doc_formfield.cpp
@@ -529,7 +529,7 @@
   }
 
   if (pValue->IsString())
-    return (pValue->GetUnicodeText() == opt_value);
+    return pValue->GetUnicodeText() == opt_value;
 
   if (pValue->IsNumber()) {
     if (pValue->GetString().IsEmpty())