AppListItemModel -> AppListItem

As previously discussed, reenaming class to reduce confusion with
AppListModel.

BUG=none
For ash/shell and c/b/sync:
TBR=sky@chromium.org,zea@chromium.org

Review URL: https://codereview.chromium.org/112593005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@242638 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 242638
Support cross-process navigations in a single subframe RenderFrameHost.

This relies on a hack of detecting when a NavigationEntry is for a
subframe RenderFrameHost, even though the navigation occurs in a
top-level RenderViewHost.  It supports cases with at most one frame,
and is only enabled when --site-per-process is used.

BUG=314791
TEST=New process is created for a cross-site iframe with --site-per-process.

Review URL: https://codereview.chromium.org/118443008

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@242639 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 242639