Added script optimize-ico-files.

chrome/app/theme/README

+PNG Images
+==========
+
 Please run src/tools/resources/optimize-png-files.sh on all new icons. For example:
   tools/resources/optimize-png-files.sh -o2 new_pngs_dir
 
 If this script does not work for some reason, at least pngcrush the files:
   mkdir crushed
   pngcrush -d crushed -brute -reduce -rem alla new/*.png
+
+ICO Images
+==========
+
+Windows ICO icons should be in the following format:
+
+* A square image of each size: 256, 48, 32, 16.
+* The 256 image should be in PNG format, and optimized.
+* The smaller images should be in BMP (uncompressed) format.
+* Each of the smaller images (48 and less) should have an 8-bit and 32-bit
+  version.
+* The 256 image should not be last (there is a bug in Gnome on Linux where icons
+  look corrupted if the PNG image is last).
+
+If you are creating an ICO from a set of PNGs of different sizes, the following
+process (using ImageMagick and GIMP) satisfies the above conditions:
+
+1. Convert each of the smaller images to 8-bit. With ImageMagick:
+
+    for f in FILENAME-??.png; \
+        do convert $f -dither None -colors 256 \
+            png8:`basename $f .png`-indexed.png; \
+    done
+
+2. Combine the images into an ICO file. With ImageMagick:
+
+    convert FILENAME-256.png FILENAME-{48,32,16}{-indexed,}.png FILENAME.ico
+
+3. Unfortunately, the 8-bit images have been converted back into 32-bit images.
+   Open the icon in GIMP and re-export it. This will also convert the large
+   256 image into a compressed PNG.
+4. Run src/tools/resources/optimize-ico-files.py on the resulting .ico file.
+
+You can also run src/tools/resources/optimize-ico-files.py on existing .ico
+files. This will run a basic PNG optimization pass.