[SystemInfo API] Rename 'harddisk' to 'fixed' for storage unit type

TBR=benwells@chromium.org

Review URL: https://chromiumcodereview.appspot.com/15846002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@202046 0039d316-1c4b-4281-b951-d872f2087c98
10 files changed