DevTools: NetworkPanel: specify content.encoding in HAR

BUG=303640

Review URL: https://codereview.chromium.org/637933005

git-svn-id: svn://svn.chromium.org/blink/trunk@184077 bbb929c8-8fbe-4397-9dbb-9b2b20218538
DevTools: make optimize_png_images.py platform-agnostic.

BUG=425468

Review URL: https://codereview.chromium.org/664373002

git-svn-id: svn://svn.chromium.org/blink/trunk@184078 bbb929c8-8fbe-4397-9dbb-9b2b20218538
[DevTools] Get rid of banned global properties usage.

This doesn't touch ui module.

BUG=424188

Review URL: https://codereview.chromium.org/662043002

git-svn-id: svn://svn.chromium.org/blink/trunk@184079 bbb929c8-8fbe-4397-9dbb-9b2b20218538