GitLab

[AW] Optimize upstream icon_webview png images resources

Following image optimizing guidelines in[1], performed near-lossless
compression using pngquant on icon_webview png files which:

reduced drawable-mdpi by 58% (7151 -> 2974 bytes)
reduced drawable-hdpi by 68% (13975 -> 4539 bytes)
reduced drawable-xhdpi by 70% (21981 -> 6611 bytes)
reduced drawable-xxhdpi by 70% (37607 -> 11439 bytes)

reduced overall image sizes by 68.33% (80714 -> 25563 bytes)

script:
```
$pngquant --version
2.12.2 (January 2018)
$pngquant */icon_webview.png -f --ext=.png
```

[1]
https://chromium.googlesource.com/chromium/src/+/HEAD/docs/speed/binary_size/optimization_advice.md#Optimizing-Images

Bug: 1045005
Change-Id: Ib45dc147fa7668c6b2e4b95132a883e7f50fba73
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2017469Reviewed-by: Andrew Grieve <agrieve@chromium.org>
Reviewed-by: Richard Coles <torne@chromium.org>
Commit-Queue: Hazem Ashmawy <hazems@chromium.org>
Cr-Commit-Position: refs/heads/master@{#734914}