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/gm/imagefiltersbase.cpp b/gm/imagefiltersbase.cpp
index 6e34713..da26d97 100644
--- a/gm/imagefiltersbase.cpp
+++ b/gm/imagefiltersbase.cpp
@@ -10,6 +10,7 @@
 #include "SkCanvas.h"
 #include "SkColorFilter.h"
 #include "SkColorPriv.h"
+#include "SkImageFilterPriv.h"
 #include "SkShader.h"
 
 #include "SkBlurImageFilter.h"