Revert "Use expected main frame size from WebViewImpl when creating a new FrameView."

This reverts commit d43def09a965260b603064b5e6916c534b74b17c, aka r185145.

Speculative revert to fix content_browsertest failures on chromeos_rel
bot.

TBR=bokan
BUG=

Review URL: https://codereview.chromium.org/717053002

git-svn-id: svn://svn.chromium.org/blink/trunk@185176 bbb929c8-8fbe-4397-9dbb-9b2b20218538