Move wm/core to wm namespace.

Also sets up new targets for wm_core, wm_core_unittests, etc.

R=sky@chromium.org
TBR=sky@chromium.org
BUG=

Review URL: https://codereview.chromium.org/196063002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@256680 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 256680
Fix peerconnection-call.html JS callEmptyThenAddOneStreamAndRenegotiate
The test now waits until the first negotiation has completed before continuing.

BUG=293125

Review URL: https://codereview.chromium.org/195143002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@256682 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 256682