Simplify MouseEventManager::HandleMouseFocus()

This patch simplifies |MouseEventManager::HandleMouseFocus()| by sharing common
code patch and utilizing early-return style for improving readability.

Bug: 919540
Change-Id: Ie6508d1c508e6d4e2b0ed589d634290e7edc8696
Reviewed-on: https://chromium-review.googlesource.com/c/1404553
Reviewed-by: Kent Tamura <tkent@chromium.org>
Commit-Queue: Yoshifumi Inoue <yosin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#621496}
1 file changed