Use validating form of IPC enum macros for blink types.

This is part of a long-running background task to remove the remaining
uses of the unchecked IPC_ENUM_TRAITS() macro.

BUG=246708
TBR=michaeln@chromium.org

Review URL: https://codereview.chromium.org/133813004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@250289 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 250289
Enabled pairing registry in the me2me host on Windows.
This CL is based on https://chromiumcodereview.appspot.com/23440071/.

TBR=jschuh@chromium.org

BUG=325567

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=249772

Review URL: https://codereview.chromium.org/139803008

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@250290 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 250290