Make image decoders faster by refactoring hot loops that fills the lines of ImageFrame.

Source/core/platform/image-decoders/jpeg/JPEGImageDecoder.cpp

 /*
  * Copyright (C) 2006 Apple Computer, Inc.
  *
  * Portions are Copyright (C) 2001-6 mozilla.org
  *
  * Other contributors:
  *   Stuart Parmenter <stuart@mozilla.com>
  *
  * Copyright (C) 2007-2009 Torch Mobile, Inc.
  *
@@ skipping 628 matching lines @@
 
 template <J_COLOR_SPACE colorSpace> void setPixel(ImageFrame& buffer, ImageFrame::PixelData* pixel, JSAMPARRAY samples, int column)
 {
     JSAMPLE* jsample = *samples + column * (colorSpace == JCS_RGB ? 3 : 4);
 
     switch (colorSpace) {
     case JCS_RGB:
         buffer.setRGBA(pixel, jsample[0], jsample[1], jsample[2], 0xFF);
         break;
     case JCS_CMYK:
-        // Source is 'Inverted CMYK', output is RGB.
-        // See: http://www.easyrgb.com/math.php?MATH=M12#text12
-        // Or: http://www.ilkeratalay.com/colorspacesfaq.php#rgb
-        // From CMYK to CMY:
-        // X =   X    * (1 -   K   ) +   K  [for X = C, M, or Y]
-        // Thus, from Inverted CMYK to CMY is:
-        // X = (1-iX) * (1 - (1-iK)) + (1-iK) => 1 - iX*iK
-        // From CMY (0..1) to RGB (0..1):
-        // R = 1 - C => 1 - (1 - iC*iK) => iC*iK  [G and B similar]
-        unsigned k = jsample[3];
-        buffer.setRGBA(pixel, jsample[0] * k / 255, jsample[1] * k / 255, jsample[2] * k / 255, 0xFF);
+        buffer.setInvertedCMYK(pixel, jsample[0], jsample[1], jsample[2], jsample[3]);
         break;
     }
 }
 
 template <J_COLOR_SPACE colorSpace> bool outputRows(JPEGImageReader* reader, ImageFrame& buffer)
 {
     JSAMPARRAY samples = reader->samples();
     jpeg_decompress_struct* info = reader->info();
     int width = info->output_width;
 
@@ skipping 88 matching lines @@
     // has failed.
     if (!m_reader->decode(*m_data, onlySize) && isAllDataReceived())
         setFailed();
     // If we're done decoding the image, we don't need the JPEGImageReader
     // anymore.  (If we failed, |m_reader| has already been cleared.)
     else if (!m_frameBufferCache.isEmpty() && (m_frameBufferCache[0].status() == ImageFrame::FrameComplete))
         m_reader.clear();
 }
 
 }