change SkClipOp to a class enum

BUG=skia:

Change-Id: I25dbe6d6b8666a2a0a7be7bdd2ae0b067868d14e
Reviewed-on: https://skia-review.googlesource.com/5718
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Mike Reed <reed@google.com>
diff --git a/samplecode/SampleIdentityScale.cpp b/samplecode/SampleIdentityScale.cpp
index ae6092a..95970e7 100644
--- a/samplecode/SampleIdentityScale.cpp
+++ b/samplecode/SampleIdentityScale.cpp
@@ -17,6 +17,7 @@
 #include "SkRandom.h"
 #include "SkStream.h"
 #include "SkTime.h"
+#include "SkClipOpPriv.h"
 
 // Intended to exercise pixel snapping observed with scaled images (and
 // with non-scaled images, but for a different reason):  Bug 1145