GitLab

- allow nodes to be clicked one beyond their text content regardless of where the node falls in the overall line
- the action node should always be the one that best fits the position as we pick the last actionable node span
- selection uses this node so selections can be made at the end of a node's text content as well

Bug: 
Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
Change-Id: I9062ec48dddeda5f85165bac4971bf858cb1ded5
Reviewed-on: https://chromium-review.googlesource.com/618291Reviewed-by: Dominic Mazzoni <dmazzoni@chromium.org>
Commit-Queue: David Tseng <dtseng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#496504}