[NaCl SDK] docs: Make the sphinx build check a warning instead of error.

The trybots don't have sphinx installed, so you can't commit-queue a docs
change.

BUG=none
R=eliben@chromium.org, sbc@chromium.org
TBR=sbc@chromium.org

Review URL: https://codereview.chromium.org/23591066

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@225002 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 225002
[DevTools, WebView] Drop the 'visible' word from WebView status on chrome://inspect

'visible' is ambiguous as it means different things for the
view manager and for a human user.

BUG=296873
R=pfeldman@chromium.org

Review URL: https://codereview.chromium.org/23889041

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@225003 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 225003