Add an unimplemented history API to WebView

This API will function as a temporary shim to enable
history functionality to move to content/renderer, without
any broken intermediate steps.

This is step 1 of 5 from http://crbug.com/357327

BUG=357327

Review URL: https://codereview.chromium.org/214723003

git-svn-id: svn://svn.chromium.org/blink/trunk@170488 bbb929c8-8fbe-4397-9dbb-9b2b20218538