Removing ContentViewCore dependencies from direct WebContents functions.

It's a follow up patch to https://codereview.chromium.org/481803004/
We already restructured WebContents functionalities from ContentViewCore.
In this patch we are removing unwanted ContentViewCore methods, so that
ContentViewCore stake holders can directly call these methods.

BUG=398263

Review URL: https://codereview.chromium.org/572013002

Cr-Commit-Position: refs/heads/master@{#299246}
32 files changed