Removing dead code in WebViewImpl.h

In patch https://codereview.chromium.org/263853008
WebViewImpl::resetSavedScrollAndScaleState() function definition was removed but not function declaration.

Review URL: https://codereview.chromium.org/670143002

git-svn-id: svn://svn.chromium.org/blink/trunk@184183 bbb929c8-8fbe-4397-9dbb-9b2b20218538