Use getContentViewClient instead of mContentViewClient

It create a new instance if mContentViewClient is null

BUG=319198
NOTRY=true

Review URL: https://codereview.chromium.org/73033002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@235221 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 235221