create imagepriv and name params

Named all parameters and made the names consistent
for documentation.

Moved SK_IMAGEFILTER_UNFLATTEN_COMMON to private file.

TBR=reed@google.com
Bug: skia:6898
Change-Id: I1343d2b16d4217088fa3bc9c40f1f4177fa32740
Reviewed-on: https://skia-review.googlesource.com/66521
Reviewed-by: Cary Clark <caryclark@skia.org>
Commit-Queue: Cary Clark <caryclark@skia.org>
diff --git a/tests/PDFPrimitivesTest.cpp b/tests/PDFPrimitivesTest.cpp
index 8c6b03c..19e4035 100644
--- a/tests/PDFPrimitivesTest.cpp
+++ b/tests/PDFPrimitivesTest.cpp
@@ -16,6 +16,7 @@
 #include "SkDocument.h"
 #include "SkDeflate.h"
 #include "SkImageEncoder.h"
+#include "SkImageFilterPriv.h"
 #include "SkMakeUnique.h"
 #include "SkMatrix.h"
 #include "SkPDFCanon.h"