[M41_2272] Explicitly specify namespace for base::CommandLine

[M41_2272] Explicitly specify namespace for base::CommandLine

Based on the original work of SeungSeop Park <sns.park@samsung.com>.
Original commit message:

This patch is necessary because 'using base::CommandLine' declaration
has been removed from base/command_line.h in chromium m41_2272.
Note that this patch can be landed before switching to the new branch.