Set is_hidden bit for background navigations

r218548 added an initial visibility state for WebContentsImpls and RenderWidgetHost(View|Impl)s and set it for cross-process navigations, but failed to set the correct initial state for in-process navigations.  This propagates the initial hidden state correctly in these places:

1.) For browser navigations, this propagates the WebContents::CreateParams::initially_hidden bit into WebContentsImpl.  Previously this went nowhere (oops!)
2.) For window.open() navigations to background tabs, this initializes the RenderViewImpl's hidden bit based on the navigation disposition.
3.) For RenderWidgetHostView impls that store their own is_hidden bit (mac, gtk and guest) this sets the initial state correctly based off of the RenderWidgetHostImpl.  The other RWHView implementations do not store their own is_hidden bool and just ask their RenderWidgetHostImpl for the bit.  I'm not sure why this is.

BUG=305437, 302574
TEST=see bug
R=jam@chromium.org

Review URL: https://codereview.chromium.org/27203004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@229428 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 229428