Disable a subtest of PPAPIPPPInstance.

BUG=329511

Review URL: https://codereview.chromium.org/101043007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@241743 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 241743