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/SampleApp.cpp b/samplecode/SampleApp.cpp
index 1acd975..8797c4d 100644
--- a/samplecode/SampleApp.cpp
+++ b/samplecode/SampleApp.cpp
@@ -36,6 +36,7 @@
 #include "SkWindow.h"
 #include "sk_tool_utils.h"
 #include "SkScan.h"
+#include "SkClipOpPriv.h"
 
 #include "SkReadBuffer.h"
 #include "SkStream.h"