Update the Web Notifications externs to the latest specs.

R=atwilson
DELTA=37 (34 added, 0 deleted, 3 changed)


Revision created by MOE tool push_codebase.
MOE_MIGRATION=6259


git-svn-id: http://closure-compiler.googlecode.com/svn/trunk@2508 b0f006be-c8cd-11de-a2e8-8d36a3108c74