[NaCl SDK] Fix off-by-one bug in http-mount.

Cached reads would return -1 when reading at the end of the file (instead of 0).

BUG=none
TBR=sbc@chromium.org
NOTRY=true


Review URL: https://chromiumcodereview.appspot.com/12379091

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@186236 0039d316-1c4b-4281-b951-d872f2087c98

native_client_sdk/src/libraries/nacl_io/mount_http.cc

@@ -418,7 +418,7 @@ int MountNodeHttp::DownloadToCache() {
 }
 
 int MountNodeHttp::ReadPartialFromCache(size_t offs, void* buf, size_t count) {
-  if (offs >= cached_data_.size()) {
+  if (offs > cached_data_.size()) {
     errno = EINVAL;
     return -1;
   }