DevTools: [SASS] extract exact property name and value ranges
The patch starts extracting exact property name and value ranges, which
makes it possible to link sourceMap entries based on the text node
start position.
BUG=
608097
R=pfeldman
Committed:
https://crrev.com/7e98d06e71e63bebefcc8b5075895680925afc52
Cr-Commit-Position: refs/heads/master@{#391443}