Use GetSelectedText() to check whether any text is selected or not.

Bug: 901439, 908762
Test: content_browsertests
Change-Id: Id8730f01db6781d7983ebbc1402176203e0b146a
Reviewed-on: https://chromium-review.googlesource.com/c/1347634
Reviewed-by: Avi Drissman <avi@chromium.org>
Reviewed-by: Sadrul Chowdhury <sadrul@chromium.org>
Commit-Queue: Yuichiro Hanada <yhanada@chromium.org>
Cr-Commit-Position: refs/heads/master@{#613366}
5 files changed