remove double '/' in download link
remove double '/' in download link

BUG=

Review URL: https://codereview.chromium.org/11030038

git-svn-id: e22621a84199d42b34715cdc089545aeedbbf23f@1428 050acbb0-2703-11df-ab0a-9f3f633ae91d

sbc100/nativeclient-sdk,sbc100/nativeclient-sdk,sbc100/nativeclient-sdk,sbc100/nativeclient-sdk,sbc100/nativeclient-sdk,sbc100/nativeclient-sdk,sbc100/nativeclient-sdk