rebaseline_server: use just skpdiff, not Python Image Library

tools/skpdiff/SkImageDiffer.h

Index: tools/skpdiff/SkImageDiffer.h
diff --git a/tools/skpdiff/SkImageDiffer.h b/tools/skpdiff/SkImageDiffer.h
index 641bbe8f8f863b4610348b5b41573564e21fc88b..63db05e49c6e3baef1af4a6e5f58d5879af70649 100644
--- a/tools/skpdiff/SkImageDiffer.h
+++ b/tools/skpdiff/SkImageDiffer.h
@@ -25,6 +25,11 @@ public:
         double result;
         int poiCount;
         SkBitmap poiAlphaMask; // optional
+        SkBitmap rgbDiffBitmap; // optional
+        SkBitmap whiteDiffBitmap; // optional
+        int maxRedDiff; // optional
+        int maxGreenDiff; // optional
+        int maxBlueDiff; // optional
         double timeElapsed; // optional
     };
 
@@ -43,11 +48,13 @@ public:
      * diff on a pair of bitmaps.
      * @param  baseline    The correct bitmap
      * @param  test        The bitmap whose difference is being tested
-     * @param  computeMask true if the differ is to attempt to create poiAlphaMask
+     * @param  computeAlphaMask true if the differ is to attempt to create poiAlphaMask
+     * @param  computeRgbDiff   true if the differ is to attempt to create rgbDiffBitmap
+     * @param  computeWhiteDiff true if the differ is to attempt to create whiteDiffBitmap
      * @return             true on success, and false in the case of failure
      */
-    virtual bool diff(SkBitmap* baseline, SkBitmap* test, bool computeMask,
-                      Result* result) const = 0;
+    virtual bool diff(SkBitmap* baseline, SkBitmap* test, bool computeAlphaMask,
+                      bool computeRgbDiff, bool computeWhiteDiff, Result* result) const = 0;
 };
 
 #endif