Remove deprecated method from WebView.

Chromium has switched from setIgnoreViewportTagMaximumScale() to
setIgnoreViewportTagScaleLimits() in crrev.com/214274.

R=jamesr@chromium.org

Review URL: https://codereview.chromium.org/21156004

git-svn-id: svn://svn.chromium.org/blink/trunk@155295 bbb929c8-8fbe-4397-9dbb-9b2b20218538