rebaseline_server: use just skpdiff, not Python Image Library

tools/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
 
@@ skipping 10 matching lines @@
  * 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() const SK_OVERRIDE;
-    virtual bool diff(SkBitmap* baseline, SkBitmap* test, bool computeMask,
+    virtual bool diff(SkBitmap* baseline, SkBitmap* test,
+                      const BitmapsToCreate& bitmapsToCreate,
                       Result* result) const SK_OVERRIDE;
 
 protected:
 #if SK_SUPPORT_OPENCL
     virtual bool onInit() SK_OVERRIDE;
 #endif
 
 private:
 #if SK_SUPPORT_OPENCL
     cl_kernel fKernel;
 
     typedef SkCLImageDiffer INHERITED;
 #else
     typedef SkImageDiffer INHERITED;
 #endif
 };
 
 #endif