Mojo: support interfaces that lack a Peer attribute

BUG=320086
R=davemoore@chromium.org, mpcomplete@chromium.org

Review URL: https://codereview.chromium.org/153583002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@249037 0039d316-1c4b-4281-b951-d872f2087c98
Blink roll 166433:166502

http://build.chromium.org/f/chromium/perf/dashboard/ui/changelog_blink.html?url=/trunk&range=166434:166502&mode=html
TBR=
BUG=

Review URL: https://codereview.chromium.org/138793007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@249038 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 249037
Update .DEPS.git

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@249039 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 249039