Allow the Chrome Remote Desktop Viewer to be used by the v2 Chrome Remote Desktop app.

This is required to allow the CRD Viewer plugin to be used by the Chrome Remote Desktop v2 applications, since v2 Apps cannot normally load "trusted" PPAPI plugins.

This work-around will be removed once the Remoting Viewer plugin has been migrated to NaCl.

BUG=252878,134216

Review URL: https://codereview.chromium.org/20905002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@225395 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 225395