Create new FPDFPageObjMark_CountParams() API.

Bug: pdfium:1037
Change-Id: I1b7035eb199f9dd1d730b0b1112aa455f0fabcc2
Reviewed-on: https://pdfium-review.googlesource.com/30870
Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Henrique Nakashima <hnakashima@chromium.org>
diff --git a/fpdfsdk/fpdf_editpage.cpp b/fpdfsdk/fpdf_editpage.cpp
index 20d8894..7a8bbabf2 100644
--- a/fpdfsdk/fpdf_editpage.cpp
+++ b/fpdfsdk/fpdf_editpage.cpp
@@ -269,6 +269,21 @@
       buflen);
 }
 
+FPDF_EXPORT int FPDF_CALLCONV
+FPDFPageObjMark_CountParams(FPDF_PAGEOBJECTMARK mark) {
+  if (!mark)
+    return -1;
+
+  const CPDF_ContentMarkItem* pMarkItem =
+      CPDFContentMarkItemFromFPDFPageObjectMark(mark);
+
+  const CPDF_Dictionary* pParams = pMarkItem->GetParam();
+  if (!pParams)
+    return 0;
+
+  return pParams->GetCount();
+}
+
 FPDF_EXPORT FPDF_BOOL FPDF_CALLCONV
 FPDFPageObj_HasTransparency(FPDF_PAGEOBJECT pageObject) {
   if (!pageObject)