make OpenCL optional for skpdiff

experimental/skpdiff/SkCLImageDiffer.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 SkCLImageDiffer_DEFINED
 #define SkCLImageDiffer_DEFINED
 
 #include <CL/cl.h>
 #include "SkTDArray.h"
 
 #include "SkImageDiffer.h"
 
 class SkStream;
 
 /**
  * An SkImageDiffer that requires initialization with an OpenCL device and context.
  */
 class SkCLImageDiffer : public SkImageDiffer {
 public:
     SkCLImageDiffer();
 
+    virtual bool requiresOpenCL() SK_OVERRIDE { return true; }
+
     /**
      * Initializes the OpenCL resources this differ needs to work
      * @param  device  An OpenCL device
      * @param  context An OpenCL context of the given device
      * @return         True on success, false otherwise
      */
     virtual bool init(cl_device_id device, cl_context context);
 
 protected:
     /**
@@ skipping 43 matching lines @@
 
     cl_device_id     fDevice;
     cl_context       fContext;
     cl_command_queue fCommandQueue;
 
 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