Switch to using aura::CursorLoader which knows how to load system, non-system
and pak cursor resources.
On Windows, cursors will be loaded via LoadCursor first if available with a
fallback to pak file if necessary (like with component builds).
On Linux, all non-system cursor resources will be loaded from pak file. Cursors
may be loaded asynchronously resulting in the default (pointer) cursor being
returned on the first request.
The cursor change can now be handled by the client with both windowed and
off-screen rendering.
Returning true from OnCursorChange will disable the default cursor change
behavior. This is functionally equivalent to the
CefBrowserHost::SetMouseCursorChangeDisabled method, so that method has been
removed.
