Auto-rebaseline for r171420

http://src.chromium.org/viewvc/blink?view=revision&revision=171420

BUG=362930
TBR=pdr@chromium.org

Review URL: https://codereview.chromium.org/236173005

git-svn-id: svn://svn.chromium.org/blink/trunk@171488 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Align srcset parsing with spec changed

This CL align the srcset parsing algorithm with recent picture spec changes.
Specifically:
* Src URL are now not part of the source selection algoritm, as per https://github.com/ResponsiveImagesCG/picture-element/pull/147
* 0w resources are ignored, to avoid 0/0 operations, and because they make no sense, as per https://github.com/ResponsiveImagesCG/picture-element/pull/151

BUG=357586

Review URL: https://codereview.chromium.org/236593003

git-svn-id: svn://svn.chromium.org/blink/trunk@171489 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Remove the srcset Runtime Enabled Flag

BUG=363039

Review URL: https://codereview.chromium.org/236753003

git-svn-id: svn://svn.chromium.org/blink/trunk@171490 bbb929c8-8fbe-4397-9dbb-9b2b20218538