update skpdiff visualization (image magnification with alpha mask)

tools/skpdiff/SkDifferentPixelsMetric_opencl.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 "SkDifferentPixelsMetric.h"
@@ skipping 29 matching lines @@
     cl_mem baseline;
     cl_mem test;
     cl_mem resultsBuffer;
     cl_mem poiBuffer;
 };
 
 const char* SkDifferentPixelsMetric::getName() {
     return "different_pixels";
 }
 
+bool SkDifferentPixelsMetric::enablePOIAlphaMask() {
+    return false;
+}
+
 int SkDifferentPixelsMetric::queueDiff(SkBitmap* baseline, SkBitmap* test) {
     int diffID = fQueuedDiffs.count();
     double startTime = get_seconds();
     QueuedDiff* diff = fQueuedDiffs.push();
 
     // If we never end up running the kernel, include some safe defaults in the result.
     diff->finished = false;
     diff->result = -1.0;
     diff->numDiffPixels = 0;
     diff->poi = NULL;
@@ skipping 101 matching lines @@
     return fQueuedDiffs[id].poi;
 }
 
 bool SkDifferentPixelsMetric::onInit() {
     if (!this->loadKernelSource(kDifferentPixelsKernelSource, "diff", &fKernel)) {
         return false;
     }
 
     return true;
 }