make OpenCL optional for skpdiff

experimental/skpdiff/SkDifferentPixelsMetric.h

+/*
+ * Copyright 2013 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkDifferentPixelsMetric_DEFINED
+#define SkDifferentPixelsMetric_DEFINED
+
+#include "SkTDArray.h"
+
+#if SK_SUPPORT_OPENCL
+#include "SkCLImageDiffer.h"
+#else
+#include "SkImageDiffer.h"
+#endif
+
+/**
+ * A 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 SkDifferentPixelsMetric :
+#if SK_SUPPORT_OPENCL
+    public SkCLImageDiffer {
+#else
+    public SkImageDiffer {
+#endif
+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:
+#if SK_SUPPORT_OPENCL
+    virtual bool onInit() SK_OVERRIDE;
+#endif
+
+private:
+    struct QueuedDiff;
+
+    SkTDArray<QueuedDiff> fQueuedDiffs;
+
+#if SK_SUPPORT_OPENCL
+    cl_kernel fKernel;
+
+    typedef SkCLImageDiffer INHERITED;
+#else
+    typedef SkImageDiffer INHERITED;
+#endif
+};
+
+#endif