Fix "narrowing conversion" errors uncovered in building with gcc 4.8

BUG=340312

Review URL: https://codereview.chromium.org/178613006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@253943 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 253943
Fix the focus issue for app launcher folder name:
1. After user change the folder name and press enter, the focus will go back to the search box.
2. When user clicks back button to navigate back top level app list grid view, the focus will go back to the search box.

BUG=344682
R=xiyuan@chromium.org

Review URL: https://codereview.chromium.org/182423002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@253946 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 253946