OS(ANDROID) should not imply OS(LINUX)

Change the config.h of blink to match the behavior in chromium's build_config.h

BUG=286645

Review URL: https://codereview.chromium.org/23691071

git-svn-id: svn://svn.chromium.org/blink/trunk@158858 bbb929c8-8fbe-4397-9dbb-9b2b20218538