Revert of Rename kPMColor_SkColorType to kN32_SkColorType.

tools/skpdiff/SkPMetric.cpp

 #include <cmath>
 
 #include "SkBitmap.h"
 #include "skpdiff_util.h"
 #include "SkPMetric.h"
 #include "SkPMetricUtil_generated.h"
 
 struct RGB {
     float r, g, b;
 };
@@ skipping 107 matching lines @@
         }
     }
     lab->l = 116.0f * f[1] - 16.0f;
     lab->a = 500.0f * (f[0] - f[1]);
     lab->b = 200.0f * (f[1] - f[2]);
 }
 
 /// Converts a 8888 bitmap to LAB color space and puts it into the output
 static bool bitmap_to_cielab(const SkBitmap* bitmap, ImageLAB* outImageLAB) {
     SkBitmap bm8888;
-    if (bitmap->colorType() != kN32_SkColorType) {
-        if (!bitmap->copyTo(&bm8888, kN32_SkColorType)) {
+    if (bitmap->colorType() != kPMColor_SkColorType) {
+        if (!bitmap->copyTo(&bm8888, kPMColor_SkColorType)) {
             return false;
         }
         bitmap = &bm8888;
     }
 
     int width = bitmap->width();
     int height = bitmap->height();
     SkASSERT(outImageLAB->width == width);
     SkASSERT(outImageLAB->height == height);
 
@@ skipping 314 matching lines @@
     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;
 }