rebaseline_server: use just skpdiff, not Python Image Library

tools/skpdiff/SkPMetric.cpp

 #include <cmath>
 #include <math.h>
 
 #include "SkBitmap.h"
 #include "skpdiff_util.h"
 #include "SkPMetric.h"
 #include "SkPMetricUtil_generated.h"
 
 struct RGB {
     float r, g, b;
@@ skipping 424 matching lines @@
         }
     }
 
     SkDELETE_ARRAY(cyclesPerDegree);
     SkDELETE_ARRAY(contrast);
     SkDELETE_ARRAY(thresholdFactorFrequency);
     SkDELETE_ARRAY(contrastSensitivityTable);
     return 1.0 - (double)(*poiCount) / (width * height);
 }
 
-bool SkPMetric::diff(SkBitmap* baseline, SkBitmap* test, bool computeMask, Result* result) const {
+bool SkPMetric::diff(SkBitmap* baseline, SkBitmap* test, bool computeAlphaMask,
+                     bool computeRgbDiff, bool computeWhiteDiff, Result* result) const {
     double startTime = get_seconds();
 
     // Ensure the images are comparable
     if (baseline->width() != test->width() || baseline->height() != test->height() ||
                     baseline->width() <= 0 || baseline->height() <= 0) {
         return false;
     }
 
     ImageLAB baselineLAB(baseline->width(), baseline->height());
     ImageLAB testLAB(baseline->width(), baseline->height());
 
     if (!bitmap_to_cielab(baseline, &baselineLAB) || !bitmap_to_cielab(test, &testLAB)) {
         return true;
     }
 
     result->poiCount = 0;
     result->result = pmetric(&baselineLAB, &testLAB, &result->poiCount);
     result->timeElapsed = get_seconds() - startTime;
 
     return true;
 }