.gitignore: Ignore ozone/.
.gitignore: Ignore ozone/.

Just like we did for .xwalk/, ignore the ozone/ directory (it also prevents
it from being deleted if one runs gclient sync with -D).

fujunwei/chromium-crosswalk,fujunwei/chromium-crosswalk,fujunwei/chromium-crosswalk,fujunwei/chromium-crosswalk,fujunwei/chromium-crosswalk,fujunwei/chromium-crosswalk,fujunwei/chromium-crosswalk,fujunwei/chromium-crosswalk,fujunwei/chromium-crosswalk