Update the memory usage estimate to 125 bytes / pixel.

Actual memory usage on a 1 MP image was 110 MiB.

Author: szabadka

guetzli/guetzli.cc

@@ -34,7 +34,7 @@ constexpr int kDefaultJPEGQuality = 95;
 
 // An upper estimate of memory usage of Guetzli. The bound is
 // max(kLowerMemusaeMB * 1<<20, pixel_count * kBytesPerPixel)
-constexpr int kBytesPerPixel = 200;
+constexpr int kBytesPerPixel = 125;
 constexpr int kLowestMemusageMB = 100; // in MB
 
 constexpr int kDefaultMemlimitMB = 6000; // in MB