Make use of base::less in base::Value

Following http://crrev.com/2944523002 base::flat_map supports
transparent comparisions. This CL makes use of this by removing now
unneccesary temporary std::string constructions from base::StringPieces.

Bug: 646113
Change-Id: Id6672b80bd706a3e3ae62c30468cd387b11ab4e3
Reviewed-on: https://chromium-review.googlesource.com/592367
Reviewed-by: Brett Wilson <[email protected]>
Commit-Queue: Jan Wilken Dörrie <[email protected]>
Cr-Commit-Position: refs/heads/master@{#491225}
3 files changed