Let WebContentsAdapter own the WebContents directly.

Flatten the ownership tree by removing WebContentsDelegateQt from the
ownership chain of the content::WebContents.

This also let WebContentsAdapter do the needed initialization work.

Change-Id: Ie652bbcad54799b66d28a4a33e627f667b1c0d28
Reviewed-by: Andras Becsi <andras.becsi@digia.com>
Get rid of WebContentsAdapter::webContents().

This isn't needed since the ownership was removed from WebContentsDelegateQt.

Change-Id: I44755966fd7681c638da083803cfde6262cb2dc2
Reviewed-by: Andras Becsi <andras.becsi@digia.com>
Ref-count WebContentsAdapter.

This is needed to handle createWindow where a WebContentsAdapter will
be created to wrap the new WebContents and will passed up through the
API. If the application doesn't handle the callback, this will allow
managing the lifetime of the WebContents more easily.

Change-Id: I40ae1973a9bdf8c3d75f9ff137228d48ed92cfb2
Reviewed-by: Andras Becsi <andras.becsi@digia.com>