If a tree lays out in the forest and no one hears it, does it reach a milestone?

And what about it's relevant repaint rects?  Are they relevant?

It turns out, no.  At least not that Chromium cared.

Remove epic dead code.

This was added by Apple for WebKit2 but never used by Chromium:
http://trac.webkit.org/changeset/129545

I removed the didFirstLayout() callback from WebFrameClient, but could not remove didFirstVisuallyNonEmptyLayout as that's currently used by Android to set the background color.

R=abarth
BUG=299834

Review URL: https://chromiumcodereview.appspot.com/25046003

git-svn-id: svn://svn.chromium.org/blink/trunk@158474 bbb929c8-8fbe-4397-9dbb-9b2b20218538