Disable view source for Developer Tools.

R=pfeldman, dgozman
BUG=334586

Review URL: https://codereview.chromium.org/130483005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@245901 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 245901