make OpenCL optional for skpdiff

experimental/skpdiff/SkCLImageDiffer.h

Index: experimental/skpdiff/SkCLImageDiffer.h
diff --git a/experimental/skpdiff/SkCLImageDiffer.h b/experimental/skpdiff/SkCLImageDiffer.h
index 6509392a9c3a00ffad1f96e1b6b101ebfa9a2849..231ea0531a90f9c6e243ab8ffa88ac15f24e1d77 100644
--- a/experimental/skpdiff/SkCLImageDiffer.h
+++ b/experimental/skpdiff/SkCLImageDiffer.h
@@ -85,30 +85,4 @@ private:
     typedef SkImageDiffer INHERITED;
 };
 
-/**
- * A OpenCL differ that measures the percentage of different corresponding pixels. If the two images
- * are not the same size or have no pixels, the result will always be zero.
- */
-class SkDifferentPixelsImageDiffer : public SkCLImageDiffer {
-public:
-    virtual const char* getName() SK_OVERRIDE;
-    virtual int queueDiff(SkBitmap* baseline, SkBitmap* test) SK_OVERRIDE;
-    virtual void deleteDiff(int id) SK_OVERRIDE;
-    virtual bool isFinished(int id) SK_OVERRIDE;
-    virtual double getResult(int id) SK_OVERRIDE;
-    virtual int getPointsOfInterestCount(int id) SK_OVERRIDE;
-    virtual SkIPoint* getPointsOfInterest(int id) SK_OVERRIDE;
-
-protected:
-    virtual bool onInit() SK_OVERRIDE;
-
-private:
-    struct QueuedDiff;
-
-    SkTDArray<QueuedDiff> fQueuedDiffs;
-    cl_kernel fKernel;
-
-    typedef SkCLImageDiffer INHERITED;
-};
-
 #endif