Change OmniboxEditModel to always use virtual URL instead of actual URL

Change OmniboxEditModel to always use virtual URL instead of actual URL

OmniboxEditModel typically manipulates the virtual URL (as defined in the
comments to NavigationEntry::GetVirtualURL()). However, there is one callsite
where it uses the actual URL (as defined in the comments to
NavigationEntry::GetURL()). Per the comment above this usage, it appears that
this usage is intended to be the virtual URL (aka the visible URL). This CL
makes the change.

To understand how the code change relates to the above description, note that
ChromeOmniboxClient::GetURL() returns the virtual URL of the visible
NavigationEntry (via WebContents::GetURL(), which itself is the same as
WebContents::GetVisibleURL()).

Review URL: https://codereview.chromium.org/1260703003

Cr-Commit-Position: refs/heads/master@{#341173}