move kTileModeCount out of TileMode enum

BUG=skia:
TBR=

Review URL: https://codereview.chromium.org/1009193002

include/core/SkShader.h

@@ -65,8 +65,10 @@ public:
         /** only draw within the original domain, return 0 everywhere else */
         kDecal_TileMode,
 #endif
+    };
 
-        kTileModeCount
+    enum {
+        kTileModeCount = kMirror_TileMode + 1
     };
 
     // override these in your subclass