Revert of It2me native messaging host: webapp implementation. (https://codereview.chromium.org/138503009/)

Reason for revert:
Broke mac build again: http://build.chromium.org/p/chromium.chrome/builders/Google%20Chrome%20Mac/builds/16217


Original issue's description:
> It2me native messaging host: webapp implementation.
> 
> The webapp implementation of the it2me native messaging is based on the me2me couterpart. But I got rid of the per-message onDone/onError callbacks because unlike me2me, all requests to the it2me host are asynchronous: direct responses to all requests are meaningless. Only the asynchronous callbacks on host state change and nat policy update need to be processed.
> 
> I verified that this is fully functional on Linux. Windows and Mac verification haven't been done and are planned after the linux work is completed.
> 
> BUG=309844
> 
> Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=248072
> 
> Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=248157

TBR=jamiewalch@chromium.org,lambroslambrou@chromium.org,sergeyu@chromium.org,weitaosu@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=309844

Review URL: https://codereview.chromium.org/150983004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@248168 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 248168