[Files.app] Fix an unexpected behavior in waitElement

This patch fixes unintentional behaviors in waitElement.
- return true without calling callback
- return false with calling callback. 

BUG=328762
TEST=manually tested

Review URL: https://codereview.chromium.org/102643005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@241289 0039d316-1c4b-4281-b951-d872f2087c98
Fix documentation for GridLayout.

No functional changes - just clarifying the parameters.

BUG=

Review URL: https://codereview.chromium.org/107303006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@241290 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 241290