Issue 3504 - Fixed: Screenshot color reduction step of the Issue Reporter is very slow

lib/child/dataCollector.js

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-2015 Eyeo GmbH
  *
  * Adblock Plus is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 3 as
  * published by the Free Software Foundation.
  *
  * Adblock Plus is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 94 matching lines @@
   let scalingFactor = screenshotWidth / copyWidth;
   canvas.height = copyHeight * scalingFactor;
 
   context.save();
   context.scale(scalingFactor, scalingFactor);
   context.drawWindow(window, copyX, copyY, copyWidth, copyHeight, "rgb(255,255,255)");
   context.restore();
 
   // Reduce colors
   let pixelData = context.getImageData(0, 0, canvas.width, canvas.height);
-  let max = pixelData.width * pixelData.height * 4;
+  let data = pixelData.data;
   let mapping = [0x00,  0x55,  0xAA,  0xFF];
-  for (let i = 0; i < max; i++)
+  for (let i = 0; i < data.length; i++)
   {
-    pixelData.data[i] = mapping[pixelData.data[i] >> 6];
+    data[i] = mapping[data[i] >> 6];
 
     if (i % 5000 == 0)
     {
       // Take a break every 5000 bytes to prevent browser hangs
       yield new Promise((resolve, reject) => Utils.runAsync(resolve));
     }
   }
 
   return pixelData;
 }