Moved guest_view_registry to GuestViewManager and made it an instance map

This change allows for the change towards moving GuestViewManager to components
and implementing an extensions specific GuestViewManager that installs extensions-specific
guest types.

BUG=444869

Review URL: https://codereview.chromium.org/1096623002

Cr-Commit-Position: refs/heads/master@{#325919}
void GuestViewBase::DispatchOnResizeEvent(const gfx::Size& old_size,
                                          const gfx::Size& new_size) {
  if (new_size == old_size)
    return;

  scoped_ptr<base::DictionaryValue> args(new base::DictionaryValue());
  args->SetInteger(guestview::kOldWidth, old_size.width());
  args->SetInteger(guestview::kOldHeight, old_size.height());
  args->SetInteger(guestview::kNewWidth, new_size.width());
  args->SetInteger(guestview::kNewHeight, new_size.height());
  DispatchEventToGuestProxy(
      new GuestViewEvent(guestview::kEventResize, args.Pass()));
}

void GuestViewBase::DispatchOnResizeEvent(const gfx::Size& old_size,
                                          const gfx::Size& new_size) {
  if (new_size == old_size)
    return;

  scoped_ptr<base::DictionaryValue> args(new base::DictionaryValue());
  args->SetInteger(guestview::kOldWidth, old_size.width());
  args->SetInteger(guestview::kOldHeight, old_size.height());
  args->SetInteger(guestview::kNewWidth, new_size.width());
  args->SetInteger(guestview::kNewHeight, new_size.height());
  DispatchEventToGuestProxy(
      new GuestViewEvent(guestview::kEventResize, args.Pass()));
}
