Preserve editing style for -webkit-tap-highlight-color on all ports that enable ENABL...

Preserve editing style for -webkit-tap-highlight-color on all ports that enable ENABLE_TOUCH_EVENTS
https://bugs.webkit.org/show_bug.cgi?id=135963

Reviewed by Andy Estes.

Currently we only preserve the CSS property -webkit-tap-highlight-color during editing operations
for iOS. Instead we should preserve it for all ports that enable ENABLE_TOUCH_EVENTS as this CSS
property isn't specific to iOS.

Also added FIXME comment with regards to the CSS property -webkit-composition-fill-color.

* editing/EditingStyle.cpp:

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@172620 268f45cc-cd09-0410-ab3c-d52691b4dbfc