Fix declaration vs. implementation ordering in NativeAppWindow{Views|Gtk}

This just reorders the functions in the NativeAppWindow interface. There are
other ordering problems but they aren't worth fixing.

Also move native_app_window.h into apps/ui/.

BUG=306535
TEST=compiles
TBR=benwells@chromium.org for file moves and trivial header path renames

Review URL: https://codereview.chromium.org/27207003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@228848 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 228848
Add failed provisional load to the tab observer.

BUG=306670

Review URL: https://codereview.chromium.org/26263006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@228849 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 228849