Disable FileManager browser_tests related to AudioPlayer which fail with Object.observe enabled

These tests caused the V8 roll to be rolled back in r256264. Disabling them
will allow Object.observe to be re-enabled by default.

BUG=351967,v8:2409
TBR=yoshiki@chromium.org
NOTRY=true

Review URL: https://codereview.chromium.org/195943005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@256706 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 256706