Make splitview drag indicators always have no overlap with shelf.

See recorded video:
https://drive.google.com/file/d/0B5I0jFeLxqIiR3dNb1M4andpb3FnZUtCMVR1VkFSa1NhaURz/view?usp=sharing

Bug: 908686
Change-Id: Id9ef51dfa6e399638a328bed6511036335a2c0c5
Reviewed-on: https://chromium-review.googlesource.com/c/1364470
Reviewed-by: Xiaoqian Dai <xdai@chromium.org>
Commit-Queue: Min Chen <minch@chromium.org>
Cr-Commit-Position: refs/heads/master@{#614560}
2 files changed