Add public method FPDFPageObj_GetType to get type of a page object.

The possible return values were already part of the public header in the
form of a set of defines.

Change-Id: I040e0f330fdd7a3cd29f74fc6ee06d122afd2dd0
Reviewed-on: https://pdfium-review.googlesource.com/3570
Reviewed-by: Nicolás Peña <npm@chromium.org>
Reviewed-by: dsinclair <dsinclair@chromium.org>
Commit-Queue: dsinclair <dsinclair@chromium.org>
diff --git a/fpdfsdk/fpdfview_c_api_test.c b/fpdfsdk/fpdfview_c_api_test.c
index b090319..fec91ef 100644
--- a/fpdfsdk/fpdfview_c_api_test.c
+++ b/fpdfsdk/fpdfview_c_api_test.c
@@ -79,6 +79,7 @@
     CHK(FPDFPage_HasTransparency);
     CHK(FPDFPage_GenerateContent);
     CHK(FPDFPageObj_HasTransparency);
+    CHK(FPDFPageObj_GetType);
     CHK(FPDFPageObj_Transform);
     CHK(FPDFPage_TransformAnnots);
     CHK(FPDFPageObj_NewImageObj);