Revert of Revert of Rename kPMColor_SkColorType to kN32_SkColorType.

tools/skpdiff/SkDiffContext.cpp

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkBitmap.h"
 #include "SkImageDecoder.h"
 #include "SkOSFile.h"
@@ skipping 104 matching lines @@
         if (alphaMaskPending
                 && SkImageDiffer::RESULT_CORRECT != diffData.fResult.result
                 && !diffData.fResult.poiAlphaMask.empty()
                 && !newRecord->fCommonName.isEmpty()) {
 
             newRecord->fDifferencePath = SkOSPath::SkPathJoin(fDifferenceDir.c_str(),
                                                               newRecord->fCommonName.c_str());
 
             // compute the image diff and output it
             SkBitmap copy;
-            diffData.fResult.poiAlphaMask.copyTo(&copy, kPMColor_SkColorType);
+            diffData.fResult.poiAlphaMask.copyTo(&copy, kN32_SkColorType);
             SkImageEncoder::EncodeFile(newRecord->fDifferencePath.c_str(), copy,
                                        SkImageEncoder::kPNG_Type, 100);
 
             // cleanup the existing bitmap to free up resources;
             diffData.fResult.poiAlphaMask.reset();
 
             alphaMaskPending = false;
         }
     }
 }
@@ skipping 215 matching lines @@
         for (int i = 0; i < cntColumns; i++) {
             SkString str;
             str.printf(", %f", values[i]);
             stream.writeText(str.c_str());
         }
         stream.writeText("\n");
 
         currentRecord = iter2.next();
     }
 }