DevTools: [CSS] eliminate styleId & propertyIndex arguments in setPropertyText

This patch modifies CSS domain of devtools protocol.
Instead of using styleId & propertyIndex in setPropertyText method to
reference actual property in OM, we now will use styleSheetId and textRange
of the property.

This patch is the first step to elimiate usage of styleId/ruleId in the
CSS domain.

BUG=341506
R=apavlov@chromium.org, jochen@chromium.org, pfeldman@chromium.org

Review URL: https://codereview.chromium.org/206543004

git-svn-id: svn://svn.chromium.org/blink/trunk@170852 bbb929c8-8fbe-4397-9dbb-9b2b20218538