base: Replace "using namespace base;" by wrapping the tests around "namespace base { ... }"
base: Replace "using namespace base;" by wrapping the tests around "namespace base { ... }"

BUG=82078
TEST=base_unittests

R=evan@chromium.org

Review URL: http://codereview.chromium.org/7000011

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@84870 0039d316-1c4b-4281-b951-d872f2087c98

yitian134/chromium,ropik/chromium,gavinp/chromium,adobe/chromium,gavinp/chromium,yitian134/chromium,yitian134/chromium,adobe/chromium,adobe/chromium,ropik/chromium,yitian134/chromium,adobe/chromium,ropik/chromium,gavinp/chromium,adobe/chromium,yitian134/chromium,yitian134/chromium,yitian134/chromium,gavinp/chromium,adobe/chromium,gavinp/chromium,ropik/chromium,gavinp/chromium,adobe/chromium,ropik/chromium,adobe/chromium,yitian134/chromium,gavinp/chromium,gavinp/chromium,adobe/chromium,gavinp/chromium,yitian134/chromium,ropik/chromium,adobe/chromium,ropik/chromium,yitian134/chromium,adobe/chromium,ropik/chromium,ropik/chromium,gavinp/chromium