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/src/effects/SkDisplacementMapEffect.cpp b/src/effects/SkDisplacementMapEffect.cpp
index 09aaf7c..14a1f66 100644
--- a/src/effects/SkDisplacementMapEffect.cpp
+++ b/src/effects/SkDisplacementMapEffect.cpp
@@ -9,6 +9,7 @@
 
 #include "SkBitmap.h"
 #include "SkColorSpaceXformer.h"
+#include "SkImageFilterPriv.h"
 #include "SkReadBuffer.h"
 #include "SkSpecialImage.h"
 #include "SkWriteBuffer.h"