Further reorganize code flow in ComputeInlineBoxPosition

This patch moves the atomic inline handling code before the block flow
handling code, so that there is no longer fall through from block flow
to atomic inline.

Bug: 771398
Change-Id: Idb4013e5616a2e81a13f4c6829c3afb2b86faa68
Reviewed-on: https://chromium-review.googlesource.com/775550
Commit-Queue: Yoshifumi Inoue <yosin@chromium.org>
Reviewed-by: Yoshifumi Inoue <yosin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#517766}
InlineBoxPosition ComputeInlineBoxPosition(const Position& position,
                                           TextAffinity affinity,
                                           TextDirection primary_direction) {
  return ComputeInlineBoxPositionTemplate<EditingStrategy>(position, affinity,
                                                           primary_direction);
}

InlineBoxPosition ComputeInlineBoxPosition(const Position& position,
                                           TextAffinity affinity,
                                           TextDirection primary_direction) {
  return ComputeInlineBoxPositionTemplate<EditingStrategy>(position, affinity,
                                                           primary_direction);
}
