I ran optimize-png-files.sh -o2 on chrome/android/java/res/.
This is result for mdpi and hdpi subfolders.

The small (~10 bytes) optimizations were ignored.

Overall: 3386 bytes saved, originally 37814 bytes -> 8.9%.

Results log:

drawable-hdpi/add_circle_blue.png: 1395 => 522 (873 bytes: 62%)
drawable-hdpi/btn_tab_close.png: 217 => 133 (84 bytes: 38%)
drawable-hdpi/google_logo.png: 6126 => 6053 (73 bytes: 1%)
drawable-hdpi/ic_content_copy.png: 275 => 225 (50 bytes: 18%)
drawable-hdpi/ic_get_app_white_24dp.png: 260 => 147 (113 bytes: 43%)
drawable-hdpi/infobar_subresource_filtering.png: 585 => 300 (285 bytes: 48%)
drawable-hdpi/ntp_signin_promo_card_single.9.png: 462 => 253 (209 bytes: 45%)
drawable-hdpi/search_sogou.png: 15545 => 15484 (61 bytes: 0%)
drawable-hdpi/settings_usb.png: 769 => 348 (421 bytes: 54%)
drawable-mdpi/add_circle_blue.png: 836 => 358 (478 bytes: 57%)
drawable-mdpi/btn_tab_close.png: 165 => 103 (62 bytes: 37%)
drawable-mdpi/ic_content_copy.png: 170 => 149 (21 bytes: 12%)
drawable-mdpi/ic_get_app_white_24dp.png: 193 => 113 (80 bytes: 41%)
drawable-mdpi/infobar_subresource_filtering.png: 499 => 272 (227 bytes: 45%)
drawable-mdpi/ntp_signin_promo_card_single.9.png: 291 => 171 (120 bytes: 41%)
drawable-mdpi/search_sogou.png: 9607 => 9583 (24 bytes: 0%)
drawable-mdpi/settings_usb.png: 419 => 214 (205 bytes: 48%)

BUG=702553

Review-Url: https://codereview.chromium.org/2750173007
Cr-Commit-Position: refs/heads/master@{#458767}