Revert of Revert of Rename kPMColor_SkColorType to kN32_SkColorType.

tools/skdiff_utils.cpp

Index: tools/skdiff_utils.cpp
diff --git a/tools/skdiff_utils.cpp b/tools/skdiff_utils.cpp
index 2f052395c8c7c18fda9ed03c94ac03503a731a28..5ca3d8085d054592146cdc35b2ffed5cc4d02d5f 100644
--- a/tools/skdiff_utils.cpp
+++ b/tools/skdiff_utils.cpp
@@ -85,7 +85,7 @@
 
 bool write_bitmap(const SkString& path, const SkBitmap& bitmap) {
     SkBitmap copy;
-    bitmap.copyTo(&copy, kPMColor_SkColorType);
+    bitmap.copyTo(&copy, kN32_SkColorType);
     force_all_opaque(copy);
     return SkImageEncoder::EncodeFile(path.c_str(), copy,
                                       SkImageEncoder::kPNG_Type, 100);