If a write is pending, just add it to the buffer. Don't trigger a second concurrent write.
If a write is pending, just add it to the buffer. Don't trigger a second concurrent write.

BUG=http://crbug.com/17991
TEST=as in bug

Review URL: http://codereview.chromium.org/160333

git-svn-id: http://src.chromium.org/svn/trunk/src@21981 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: bce4423aa23270c6a75e30f03bbcbcb2681fc8cf
meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser