Move SelectionTemplate::is_handle_visible_ to FrameSelection

This patch moves |is_handle_visible_| to |FrameSelection| from |SelectionTemplate|
since handle visibility is used only for setting |FrameSelection|, hence it is
a redundant member variable of |SelectionTemplate|.

Bug: 742093
Change-Id: I3add4da3844fb40be34dcb4d4b46b5fa6fed1d7e
Reviewed-on: https://chromium-review.googlesource.com/595389
Commit-Queue: Yoshifumi Inoue <yosin@chromium.org>
Reviewed-by: Xiaocheng Hu <xiaochengh@chromium.org>
Reviewed-by: Kent Tamura <tkent@chromium.org>
Cr-Commit-Position: refs/heads/master@{#491660}
void DispatchInputEventEditableContentChanged(
    Element* start_root,
    Element* end_root,
    InputEvent::InputType input_type,
    const String& data,
    InputEvent::EventIsComposing is_composing) {
  if (start_root)
    DispatchInputEvent(start_root, input_type, data, is_composing);
  if (end_root && end_root != start_root)
    DispatchInputEvent(end_root, input_type, data, is_composing);
}

void DispatchInputEventEditableContentChanged(
    Element* start_root,
    Element* end_root,
    InputEvent::InputType input_type,
    const String& data,
    InputEvent::EventIsComposing is_composing) {
  if (start_root)
    DispatchInputEvent(start_root, input_type, data, is_composing);
  if (end_root && end_root != start_root)
    DispatchInputEvent(end_root, input_type, data, is_composing);
}
